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THE 

General Electric Review 



VOLUME XIII 



1910 




PUBLISHED BY 

GENERAL ELECTRIC COMPANY 

SCHENECTADY, N. Y. 






I 

V, /3 




VOL. XIII NO. 



I opyright /.'<"." 
by General Electrii I ompany 



ANUARY. t'Mii 



CONTENTS 



Editorial 



The First Important Hydro-Electrical Development in Southern Asia 

By II. P. Gibbs 



Power Factor Regulators 



By H. A. L vyi oi i. 



14 



Commercial Electrical Testing, Part III 

By E. F. Collins 



17 



High Voltage Power Transformers of Large Si/.e 

By E. R. Pearson 



t> 



Transmission System of the Southern Power Company 

By John Liston 



24 



Gas-Electric Motor Car Self Contained Type 

By A. W. |om s 



30 



Standardization Rules of the A.I.E.E. 



\\\ I )k. C. P. Steinmetz 



54 



Rosenberg Generators 



By J. L. II \u 



59 



Transmission Line Calculations, Part IV ... 

\\\ Mil roN YV. Franki i.\ 



4.5 



Exhaust Fan Blowers for Residence Furnaces 

\>,\ R. !■:. Barker 



45 



Transmission Line Constants, P ■! \'II 



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With the present issue, the Review enters 
upon the third year of its circulation outside 
of the organization of the General Electric 
Company. Its reception by the electrical 
fraternity at large, and the support it has 
received have been most gratifying. With 
the new year more space will be devoted to 
distinctly practical articles, while theoretical 
articles will be restricted to those that have a 
direct bearing upon everyday practical en- 
gineering. The latest developments in the 
electrical engineering practice, new machinery, 
discoveries and inventions will be described 
and illustrated. 

A modem manufacturing concern of the 
magnitude of the General Electric Company 
is a distinctly educational institution and 
partakes of many of the more important 
characteristics of a university. First, there 
are the student courses composed largely of 
graduates of technical schools and colleges 
who attend for the purpose of obtaining a 
practical knowledge of actual operating con- 
ditions with a greater variety of commercial 
apparatus than was possible with the com- 
paratively limited equipment of the college 
laboratory. 

The second feature of similarity lies in the 
research work that is carried on in the various 
laboratories. Few, indeed, are the univer- 
sities that can devote such enormous sums 
as arc annually expended by a large manu- 
facturing company in purely scientific re- 
search, and there are few where the technical 
work is of a higher order. Many of the in- 
vestigations carried on in laboratories of 
manufacturing plants would, if pursued in 
those of a university, entitle tin investigator 
to the higher graduate degrees. 




A third feature of similarity to the uni- 
versity is the dissemination of information in 
printed form. As the large university prints 
its theses, monographs and pamphlets, so 
the manufacturing concern publishes the 
results of recent development and improve- 
ments in engineering methods and practice, 
describing new apparatus which must be 
brought to the attention of the engineering 
fraternity, and setting forth its use, its 
characteristics, and its advantages. Herein 
lies the function of the General Electric 
Review — it is the medium for dissemina- 
ting this information to the engineering 
profession. 

Being in close touch with the experts of the 
General Electric Company, each of whom is 
in advance of the latest developments in his 
own line, the Review possesses exceptional 
opportunities for securing early and accurate 
information in practically every branch of 
electrical activity. For this reason, it can 
furnish information a year or more in advance of 
its appearance in the text books and elsewhere. 

Of the series of articles on practical sub- 
jects scheduled for the coming year, one in 
particular, on the diagnosis and remedy of 
t roubles with alternating current apparatus, 
should be of special value to the construc- 
tion engineer, to the operator, to the 
central station man, the consulting engi- 
neer, and the student. Little has been 
written on this important ubject, and that 
little is mostly scattered through varum 
domestic and foreign magazines and books. 
We hope to make this series complete and to 
so arrange it that if a piece of alternating 
current apparatus goes wrong, the difficulty 
can be immediately located. 



GENERAL ELECTRIC REVIEW 




Mr E. B. Raymond, 
General Superinten- 
dent of the Schenec- 
tady Works, will leave 
the employ of the Gen- 
eral Electric Company 
on January -"1st to 
accept the position of 
Second Vice President 
of the Pittsburg Plate 
Glass Company, and 
take charge of their 
manufacturing. 

Mr. Raymond was 
born in Somerville, 
Massachusetts, and 
pursued his prepara- 
tory education in 
the High School of that place. He received his 
university education at the Massachusetts Institute 
of Technology, from which institution he was 
graduated in 1890, and- the same year entered 
the employ of the Thomson-Houston Company, at 
Lynn, where he devoted two years to practical work 
and then entered the Railway Department to 
take charge of experimental railway work Mr 
Raymond later entered the Calculating Depart- 
ment, under Mr. 11. F. Parshall, and when that 
department was discontinued at the time of the 
combination of the Thomson-Houston and Edison 
companies, became Assistant Engineer of the 
Chicago office, where lie was engaged in con- 
struction work and in investigating operating 
troubles. 

In the spring of 1895, Mr. Raymond came to 
Schenectady in the capacity of General Foreman 
of the department attending to erecting, testing, 
and the preparation oi apparatus for shipment. 
Mr. Raymond was appointed to his present position 
of General Superintendent ol the Schenectady 

Works in 1903, at which time the position was 
created. The duties in this position are defined 
in the following notice which was published at 
that time: 

"In the absence of tin- Manager, the General 
Superintendent will be tin- ranking officer in ch; 
of the works. 

"Foreman will report to and be governed by 
instructions from the General Superintendents 
office in matters pertaining to electrical and 
mechanical te ting and inspect ion of apparatus and 
materials, corrections tit defects thai develop in 
manufacture, suggested changes in methods or 
design of apparatus, operation of machine tools, 
readjustment of facilities and help, as requirements 

may arise, shop discipline and other matters 

relating to the economical operation or general 
condition of departments." 

With the departure of Mr. Raymond, the General 
Electric Company will lose one of the most able 
and popular members of its technical staff While 
a rigid disciplinarian, he commands both the 
respect and affection of his men, all tit whom have 

learned that with the General Superintendent they 

are alw ay ■ sure i if a ■ |uare deal. 

Mr Raymond is the author of a number ol 
monographs on electrical and mechanical subjei 

beside, two text 1 ks that are used in various 

technical colleges. 




Dr Ernst Julius 
Berg, who for a num- 
ber of years has been 
recognized as one of 
the leading engineers 
of the General Elec- 
trii < a impany, recent- 
ly act e] it el i he posi- 
| tion ot Professor ot 
j Electrical Eng 
ing and Head of the 
1 >r] iartment at the 
University of Illinois. 

Dr. Berg was horn 
at i >stersund, Sweden, 
in which country he 
resided until he reach- 
ed his majority. His 
early education i 
received in the High 

Scl 1 ol his native town, anil his technical 

education at the Royal Institute of Technology 
in Stockholm, from which he was graduated in 
1892 with the degree of Mechanical Engineer. 
Upon completing his university course. Dr. Berg 
tame to Amenta and shortly thereafter entered 
the employ of the Thomson-Houston Company. 
Here his technical knowledge and manifest ability 
as an engineer was immediately recognized, and 
from a relatively subordinate position, he rapidly 

advanced to that of Dr. Steinmetz's assistant anil 
chief ( ' iad juti ir 

In the design and development of alternators, 
motors, rotary converters, and other alternating 
current apparatus; and in the solution of such 
problems as those arising from the use of the 
alternating current for railway operation, the 
parallel operation of alternators, the hunting ot 

rotaries, etc., etc., Dr Berg rendered particularly 
effective and valuable work He contributed 
largely to the successful development of the steam 
turbine. For a number of years Dr Berg has 
acted in the capacity of Consulting Engineer with 
the General Electric Company To him were 
taken many of the more intricate and difficult 
problems 

Dr. Berg is the author of numerous papi 
engineering subjects, and his treatise on the trans 
mission and utilization of electrical energy is a 
recognized standard. He also collaborated with 
Dr. Steinmetz in the preparation of the tatter's 
well known "Alternating Current Phenomena" 
Foi the past two years he has held the position ot 

Consulting Professor of Electrical Engineering at 
Union University and recently received the degree 
of Sc. I), from that institution. 

A first-class practical engineer is a man diligently 
sought alter m these days; first das-, theoretical 
men who understand the mathematical theory of the 
science are more infrequently met. but the man who 
can combine these gifts who is both a high grade 
practical engineer anil a mathematical technician, — 
and w ho can use his theory in the practical engineer- 
ing work is exceptional indeed. Finally, the one 
who, while possessing these characteristics of theo- 

retical knowledge combined with practical engineer- 
ing abilit) can convey his informatioi ers — 
who in other words possesses the qualifications of i 
her is a r,jr,i avis. Such a one is Dr. Berg 



THE FIRST IMPORTANT HYDRO-ELECTRICAL DEVELOPMENT 

IN SOUTHERN ASIA 
By H. P Gibbs, M .A.I.E.E. 



hv 



The Undertaking 

In 1899, having decided to develo] 
draulic power in tin- vicinity of th< 
village of Sivasamudram for the sup- 
ply ol electric current to the several 
I mining companies on the Kolar 
gold field ninety-two miles away, the 
Govemmenl of Mysore despatched 
A Ji ily de Li ithbiniere, Royal 
Engineer (loaned to the State of 
Mysore by the Imperial Govern 
ment), to Europe and America for 
the purpose of arranging suitable 
contracts for the equipment and 
erection of the power plant, and for 
the utilization of the available pi iwer. 

As such work was an entirely new- 
departure in India, Capt. Lothbiniere 
first made a tour of Europe and 
America, visiting the plants of nu- 
merous manufacturers to ascertain 
which company, in the matter of 
lerience and facilities, was best 
qualified to carry through such a 
Contract. A decision was made in 
favor of tlie General Electric Company of 
America for the complete electrical work, 



agreed to install its portion and complete one 
year's successful i iperation prior to accepanetc 
on the part of the Government. 





Fig. 1 The Cauvery Falls 

including generation, transmission and distri- 
bution, and Escher Wyss, oi Zurich, for the 
hydraulii turbii es Each of these companies 



Fig. 2. Bridge at Sivasamudram 

Arrangement was made with the firm of 
Messrs. John Taylor and Sons, on behalf of t In- 
several mining companies, for the con- 
sumption of a lit t le ( iver 401 H I In >rs< ■ | lower. 

The Head Works 

At a point approximately two miles 
above the Cauvery Falls and well above 
the swiftly descending rapids, a 1"\\ 
diverting dam 4:2 ft. in height and 390 It . 
in length was built of granite masonry, 
on a river bed of hard dolerite trap 
ruck. This dam was built for the ex 
press purpose of diverting the entire 
supply of water to the channels during 
low water pern ids. 
Intake Channels 

The entrance to the two channels is 
equipped with suitable gati ; foi egu 
lating the flow of water, and, in addition 
with a scouring sluice for preventii 

undue accumulation of silt in front "I 
the channel i ipenings. 

Channels 

There an- two parallel channels winch 
follow the natural contour "i the country, 
s.> that, although the distance down the 
river from head works to power house is but 



6 



GENERAL ELECTRIC REVIEW 



2.65 miles, the channels are 3.375 miles in 
length. These two channels, when filled to 
a depth of 6.3 ft., pass 560 cubic feet of water 
per second, which quantity is sufficient to 



For the original plant, three penstocks 
were installed, each supplying two 1250 h.p. 
turbines, while subsequently each turbine 
has been supplied from a separate pipe. The 




Fig. 3. Penstock Forebays 



develop IS, 750 h.p. at the turbine shafts. 
The normal gradient of the channels is 0.2 ft. 
in 1000 ft. For a distance of 1400 feet, the 
channels were cut through a spur of horn- 
blende shist and were narrowed to a width of 
12 feet with vertical sides, the slope or grad- 
ient being increased to 0.6 in 1000. 

Forebays 

The two channels terminate in a forebay 
which is built in two sections, one for the 
original installation of 6000 
h.p. and the other for the first 
extension of 5000 h.p. Re 
cently a second extension has 
been made, increasing the 
capacity of the plant by 2000 
h.p., and making a total of 
13000 installed electrical 
horse-power in generators. 

The intake chambers for the 
penstocks are protect ci I mm 
debris by the usual iron rack 
and are regulated by gates of 
sheet iron on angle frames 
operated by hand wheels. 

Penstocks 

Each penstock is equipped 
at the top with an ordinary 
gate valve for individual con- 
trol. Each pipe has two expansion joints and is 
supported at the bottom by a firmly anchored 
thrust block located just outside of the power 
house wall. 



penstocks are located on an incline having a 
slope of 1 in 2 for about half way. and 1 in 3 
for the remainder of the distance. The 
average length of the penstocks is 920 feet, 
with an effective head of 3S2.5 feet. 

The larger pipes are built in three sections, 
with diameters of 48, 45 and 42 ins. and 
respective thicknesses of ^. } and ^ in. The 
smaller pipes are built in four sections, the 
differenl sections having diameters of 3t>, :::;. 




i)*5>- *£». 



Fig. 4. Channels Through Rock Cutting 

30 and 27 ins., and respective thicknes 

°f &• i> i an 'l v: m - The velocity of flow at 
tin- thrust blocks under norn al full load con- 
ditions is 7.33 feet per second. 



HYDRO-ELECTRICAL DEVELOPMENT IX SOUTHERN' ASIA 



Turbines 

As stated before, the turbines were built 
by Messrs. Escher Wyss, of Zurich, each 
turbine having a capacity of L250 h.p. at 
300 r.p.m., with a water consumption of 'AT', 
cu. ft. per second. An interconnection between 
penstocks is made in the power house with a 
10 in. pipe, which also serves the purpose of an 
exciter main. A similar connection from this 
pipe to the hydraulic regulators is made for use 
in emergencies, while the ordinary regulator 
supply is obtained from a separate service 
main of 10 in. diameter leading from the 
forebay, at which point settling tanks are 
provided to supply clear water in order that 
the wear of regulator valves and moving 
parts, due to gritty substance usually carried 
in the river water, may be avoided. 

Regulators 

Each turbine is equipped with two jaw 
nozzles, and the regulation is accomplished 
as follows: Each nozzle tongue is pivoted 
near its center, and the tendency to open, 
due to pressure underneath the tongue, is 
resisted by a corresponding pressure on a 
piston linked to the end of the tongue on 
the side of the fulcrum opposite to that on 
which the first mentioned pressure is exerted, 
The pressure on the top side of the piston is 
automatically varied by a regulating valve 
operated by fly-balls, allowing the nozzles 
to open and close according to requirements. 



Fiti. 5. Penstock Gates and Switch House 

This regulator works well under condi- 
tions <>t flat load curve, but is naturally slow- 
in responding to large and suddei fluctuations. 



The governor is equipped with a hydrau- 

lically operated automatic relief valve, so 
that undue rise of pressure in the system is 




•"*' -•— ' 







Fig. 6. General View of Development at Power House 

entirely eliminated when sudden shut-offs 
occur. This relief system has always proved 
reliable and efficient. 

Exciters 

The generating station is equipped 
with three turbine-driven and two 
motor-driven exciters, each of 75 kw. 
capacity, 110/1 lo volts. 

The generators consist of eleven 
720 kw. units, and one 1500 kw. unit, 
all of which are driven at 300 r.p.m. 
and operated at '2 17.'! volts, full load 
normal conditions. The stationary 
armatures are so arranged that they 
can be conveniently jacked along the 
base until clear of the revolving field, 
thus permitting of ready access to all 
parts. Up 1" tin- present, however 
(seven years' service), it has never 
been necessary i" shift any of them. 
Each generator is supplied with a 
panel equipped with nil switch, am 
pere meter, and synchronizing lamps. 
These swindles are for use in emer- 
gencies only, as ordinarily the operation is 
handled from the Step-Up station, inn feel 
above and 1200 feel away. 



GENERAL ELECTRIC REVIEW 




Fie. 7. Generating: Units 

The separation of the generating station 
and transformer house was made in accord- 
ance with the wishes of Government officers, 
as it was thought that men working above 
would be much less subjed to malaria than 
those working in the generating station below 
However, it has since been found that such 
an arrangement was unnecessary- 



danger, and now 
fever eases among 
the staff are excep- 
tional. 

The field and ar- 
mature cable of each 
machine are con 
nected by individual 
cables to the low 
tension switchboard 
apparatus above. 
These cables, which 
are paper insulated 
and leaded, are car- 
ried on projecting 
stone shelves at the 
sides of a vent 'dated 
masonry duct, i See 
illustration page 2 

Low Tension Work 

The low tension 
switchboard is so ar- 
ranged that all 2000 
volt connections are 
confined to the base 
meiit . while low ten 

sion currents only are carried above, where 

the operator stands on watch. 

General Electric Type TA regulators are 

used to good effect and with satisfactory 

results for regulating the voltage 

Alter a thorough system of metering and 

control, the current is carried along to the 

low tension side of eleven banks of General 





Fie- 8. Motor Driven Exciter 



Fie. 9. Turbine Driven Exciter 



The entire site was at first very much 
mfested with fever bacteria, but gocd water 
supply, drainage, sanitation, and clearing of 
undergrowth have combined to minimize the 



Electric transformers; eight of these banks, 
each consisting of three single-phase 375 kw.. 
2173 35000 volt, air blast transformers, 
supplying the Ivolar service; two banks, 



HYDRO-ELECTRICAL DEVELOPMENT IX SOUTHERN ASIA 



each of three 150 k\v., 
2173/35000 volt, oil cooled 
transformers, furnishing 
current for the Bangalore 
mines; anil one bank of 125 
kw., 2173/25000 vol1 . oil 
cooled transformers, sup- 
plying the service at Mysore. 
It will be noted that the 
latter bank delivers potential 
at 25000 volts instead of 
35000. as for the ol her 
service. 

High Tension Work 

Bach bank i if transfi irmers 
is equipped on the high ten- 
sion side with a group of 
three single pole double 
break oil switches set in 
masonry compartments, and 
can be isolated from the high 
tension bus-bars by means 
of knife switches. Each out- 
going line is controlled by 
an automatic motor-oper- 
ated three-] Mile ■ wit eh of the standard ( icncral 
Electric type. These switches have proved 




Fig. 10. Step-Up Station 



provide a convenient means ol isolating 
latter for examination or adjustment. 



the 



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w 



^r 



•o 2 • 



mm 



f 



j 




Fig. II, Exciter Panel 



Fig. 12. Low Tension Switch Compartments 



entirely satisfactory. Knife switches are 
installed on both sides of the oil switches to 



The lightning am ire ol the standard 

oil Electric multiplex type and are 



10 



GEXERAL ELECTRIC REVIEW 



located in the towers of the high tension 
outgoing lines. Suitable choking coils are 
also provided. 

The lines enter through plate glass set in 




Fig. 13. Step-Down Station 

suitable frames, each glass having a six 
inch hole in its centre. These entrances have 
proved very satisfactory. 

Line Construction 

There are three 
separate pole lines 
for the Kolar ser- 
vice. Two of these, 
as built during the 
first installation 
period, are made up 
m) thirl een fool 
lengl lis of ex1 ra 
heavy seven inch 
hydraulic pipe, and 
a seven inch square 
timber top seven- 
teen and a half feel 
long. The timber 
is let into i lie round 

Socket twenty-one 
inches, and the pole 
is then set six feet 

in i lie ground. This 
pole is expensive 
ami deteriorates 
rapidly due to dry 
n n wit hin t he iron 

Socket . Tlll'Se t WO 

lines carry No. copper wire supported on 
single piece, five petticoat, white porcelain 



insulators made by Richard Ginori of Milan, 
Italy. The pins are galvanized iron and 
are secured with portland cement. The dis- 
tance of transmission is ninety-two miles. 

During the third installation period, 
a third circuit was built of Xo. 000 
copper wire carried on wrought iron 
poles with angle-iron cross arms and 
Locke three part brown porcelain 
insulators. 

In special work, spans up to 1620 
teet have been built, using standard 
insulators and 6 strand hard drawn 
copper cable on a hemp core. 

The Kolar gold field transmission 
lines are equipped with two section 
stations, dividing the three circuits 
into nine sections. These section 
houses are equipped with lightning 
arresters, and knife and oil switches. 
Here the lines can be connected 
straight through, independently or in 
parallel, and any section can be con- 
veniently cut out for repairs without 
disturbing the general service. These 
station sites afford headquarters for the line 
inspectors and greatly facilitate the location 
of line trouble. 




Fig. 14. High Tension Line Entrances to Step-Up Station 



Sub-station 

The power is received 



at the step-down 



HYDRO-ELECTRICAL DEVELOPMENT IN SOUTHERN ASIA 



11 



station at approximately 30000 volts and 
reduced to 2300 volts, which is the normal 
pressure of the. distributing mains. 



Kolar gold field, 9000 h.p. from the Cauvery 
supply is employed in general mining opera- 
tions, including the driving of air compressors, 





The Maharaja of Mysore (on left) and the late Dewar, Sir Sheshadri Iyer 



The principal feature of interest in this 
sub-station is a one-thousand kilowatt syn- 
chronous motor running idle with heavily 
■1 field. The leading current provided 



mills, stone breakers, work-shops, cyanide 
works, pumps and electrical hoists. The 
hoists are both above and below ground and 
are used in sizes up to 400 h.p. These hoists 





Fie. 15. Special Construction 

by maintains the power factor at the 
centre of distribution at from 0.91 to 0.93 
Withoul this machine in circuit, the power 
factor averages 0.82. The advantage to be 
derived from this se1 in the matter of regula- 

; f the system is obvious. 

the several mining prope ies of the 



Fig. 16. Standard Construction 

are driven by 3000 voll three pha :e induction 

motors i on1 rolled by re iis1 ance in I he 

circuit Then- operal < m ha - pro^ ed to be 

satisfactory and e< 

winding ii from a 3000 fool level, carrying 

a load of rock of 2 I 2 tons al u»^n feel per 

minn 



12 



GENERAL ELECTRIC REVIEW 



Financial 

The original arrangement that the Govern- 
ment should install all distribution plants 




Fiji. 17. Special Construction 



Fifth year, up to . €24 per h.p. year 
Five following years 10 

It may here be said that of the first year's 
payment of £29, £11 was to recoup the 
Government for its expenditure on the 
distribution plant; so that the power payment 
was really £1S, as in the second, third 
and f ourt h years. 

The agreement as regarded the power of 
the second installation was the same as 
thai of the first, except that the mines in- 
stalled their own distribution plant and paid 
at the rate of £1S for the first year's 
supply. The agreement for the third in- 
stallation provided for supply at the rate 
of £10 from the outset. 

The result from the Government's point of 
view is highly satisfactory, although the 
mining companies concerned have prof- 
ited to a considerably greater extent, owing 
to the necessity of an extremely long carriage 
of an inferior class of coal on which they were 
previously dependent. 

Local Features 

During the earlier construction period, 
work of such description was entirely new 
p. the local people, which fact made it 
exceedingly difficult for the original con- 
struction staff; but the General Electric 
Company had chosen well, and sent able, hard 
working men for this special undertaking. 
with the result that the work was expedi 
tiously carried out in spite of many obstacles. 



and operate the same for a 
period of one year prior to 
acceptance by the mit 

applied only to the lirst instal- 
lation. This included all 
distributing lines. motors. 
pressors, pumps, hoists, 
belts, ropes, buildings 
fi tundal i' hi . 

The mining ci impanii - 
ed to pay for t he si rvice 
on a Hai rate, based on the 
normal lull li iad c< msumption 
of motors. Therefore, it is 
perhaps needless to say thai 
the load factor of the system 
is a remarkably high one. 

The agreement covered ten 
years payment to be as 
follows : 

First year £29perh.p. year 
Three follow- 
ing years is 




Fig. 18. 400 HP. Electrical Hoist at Ovreeum 



HYDRO-ELECTRICAL DEVELOPMENT IX SOUTHERN ASIA 



13 



Huge trains of bullocks mighl be regularly 
seen slowly wending their way along the ho1 
and dusty 30 mile road, carrying the heav) 
machinery from the railway to the power 
house site, while the mighty elephant, ever 



London, Agents for the Kolar Gold Field 

Mines. 

In closing, it will no1 be amiss to say thai 
when this development was planned, there 
wen 1 at t few similar undertakings on record, 




Fig. 19. Team of Bullocks 



ready, was frequently requisitioned to pull 
1 ou1 i if difficull situations. 
His Highness, the .Maharaja oi Mysore, 
and his able adminisl rato'rs, have often and de 
servingly been the recipients ol coi gratulation 



so that the credit due to the above mentioned 
people is undoubtedly greater than would 
at first appear when considered from a 
present-day standpoint . 

The General Electric Company assumed so 



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4 

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y. > 




WrAw^\ 


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f&C.' H 


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and praise for their pluck 
prise in carrying ou1 i his mo 

illation, which was made pi ssible through 

ir sightedness and heart) i i <p< ration 

of the firm of Messrs. John Tayloi & Sons, of 



Fig. 20. The Mighty Elephant 

and ent( ' 



, mi asureol responsibility thai any failure 
must have been mosl severely fell by i'. : bu1 as 
will be evident from the pre. . i raphs, 

the entire undertaking has proved a pracl ii 
unqualified success for all i 



14 



GENERAL ELECTRIC REVIEW 



POWER FACTOR REGULATORS 



By H. A. Laycock 



It has become to be generally conceded 
that in cummercial power and lighting work 
of the present day synchronous condensers 
are an absolute necessity to the central 
station manager, in order that the dead loss 



SuS 3ars 



?rU 






Current 7ransfo 



L-wvw — ' 



f^otent/o/ — •-..... 
Transformer fW*~ 



A C 

Genera£ar\ 



Generator 
rheostat 



/les/stonce 



fxc/ter 
/?neostat 



£*C'ter. 







Sttt— 




_ _ ftelay Contact s 



^MO'/n Contacts 

■O c. Magnet 
C Magnet 



necessary. This having been accomplished, 
the first and simplest method for the instal- 
lation of a power factor regulator is shown in 
Fig. 1. This connection is identical with 
that of a voltage regulator connected to an 
alternating current generator; in this case, 
however, one of the standard voltage reg- 
■"•■ ulators is connected to a synchronous 
motor and improves the voltage of the 
line by increasing or decreasing the ex- 
citation on this synchronous machine, the 
cycle of operation being as follows: 

Should the power factor tend to de- 
crease at some point along the line, or 
at a point where the motor is connected, 
the voltage will of course have a tendency 
to fall, due to the low power factor 



—/?e/ay Magnet 



-r~or Acf/usOng 
COm/oensot <ng 

Wma/ng 
^/fevers/ng 

S*v,tch 



-Conaense^ 



Fig. 1. Connections ofVoltage Regulator for Maintaining 
Constant Power Factor on Line 

ol power due to wattless current occasioned 
by heavy inductive loads may be eliminated. 
For this reason, synchronous motors an 
being installed on the majority of systems 
even though in certain cases they have to run 
lighl . as the reduction in the cost of delivering 

er and the improvement in the volta 
regulation of the systems more than compen- 
iate for the cost of the machines. However, 
in order that this regulation may be accurate- 
ly obtained without the attention of an 
operator an automatic regulator should be 
employed. This article describes two forms 
of regulators that are arranged for power 
factor work. It docs not matter materially 
whether the synchronous motors are running 
light, driving direct current or alternating 
current generators, or being used for power 
work, as driving conveyors, hoists, etc. 

Plants in which < ulation is desired 

should always have the generators equipped 
with vol ulators; so that the first step 

is to obtain a constant voltage at the 
power station and thus relieve the synchro- 
nous condenser from doing more work than is 




Fie. 2. Power Factor Regulator 



'OWER FACTOR REGU I.ATORS 



15 



conditions. But the alt (.■matin;; current 
regulating potential magnel is connected 
across the terminals of the motor, and thus 
when this voltage tends to fall the float- 
ing contacts are closed, which operation 
in turn closes the relay contacts, and 
builds up the exciter voltage. This 
increase in exciter voltage over-excites 
i hi fields of the synchronous motor and 
the power factor of the line, 
.it the voltage is maintained con- 
it at this point , 
By referring to connections in Fig. 
1, it will be seen that the current trans- 
former can be used if desired to over- 
compound or over excite the motor still 
in order to give the line a lead- 



This regulator is designed with a safetj 
stop, so that if desired the amount oi exci 
tation current that the motor will receive can 




HMjassGBfiGfiEl 



Fig. 3. U Relay Voltage Regula'or for Power 
Factor Regulation 

ing current. 'Phis feature is especia 
vantageous where heavy fluctuate 
inductive load occur between the 
station and center of distribute t. 




lly ad- 

tns ot 
central 






Fig. 4. Single Relay Voltage Regulator for Power Factor Regulation 

be limited, thus making the machine safe 
against injury from excessive excitation. 

Almost any number of these motors and 
regulators can be installed on a transmission 
line provided they are located far enough 
aparl to secure sufficient reactance between 
the motors to insure parallel operation with 
out hunting. 

Figs. 2, 3 and 4 show the front views oi the 
different types oi TA regulators whii h can 1" 
used for improving power factor. 

It will be noted that this arrang menl oi 
regulation does not hold a COnStanl power 
factor on the synchronous motor bui rej 
lates the motor to help hold a constant 
pow er factl >r on t he line. 

CONSTANT POWER FACTOR REGULATOR 

The appearance oi thi "it power 

r regulator is shown in Fig 2, while 

Fig. 5 shows the connections ol thi apparatu: 



16 



GENERAL ELECTRIC REVIEW 



to a synchronous motor and exciter. In this 
apparatus, the control magnet consists of two 
stationary potential coils and one movable 
coil, which, with unity power factor, merely 



of the voltage regulator, and since the con- 
tacts are operated at a high rate of vibration, 
absolutely perfect results can be obtained 
within the capacity of the motors and exciters. 




Fig. 5. Connections of Power Factor Regulator 



floats between the potential coils, the motor 
under these circumstances receiving a certain 
predetermined excitation. 

The action of tin' regulator becomes evident 
from inspection of the vector diagram, Fig 6; 
I,, I 2 , or I a is the current per phase. E,. E, 
or E 3 is the corresponding e.m.f. Assuming 
that the current coil is m circuit with the 
phase designated I.,; it is then evident that 
if the current . lor example, lags by the value I„ 
or I ,, the phase relations bet ween the currenl 

9 
in 1 he current coil and that in the potential coils 
must necessarily change. A magnetic action is 
thus set up between the coils towhichthemov 
able current coil responds, closing the main 
contacts. This closing of the main contacts 
causes the relay contacts to close, thus in- 
creasing the excitation of motor and bringing 
th( power factor back to unity, or to the 
point where the coils are balanced. 

If instead of lagging, the currenl should 
become leading, the above cycle, of course, 
will be reversed; the current coil then moving 
in the opposite direction, opening the main 
contacts, and thus the relay contacts, and 
reducing the excitation of the motor. 

If the regulator is set for unity power 
i.tcior. t he cyel ( - of , iperation is similar to that 



In addition to maintaining unity power 
factor, it is also possible, by raising oj lower- 
ing the current coil and thus changing its 
relation to one or the other of 1 he potential 




/,VgIs Current per phase 

£i '£^'£3 Correspor?d/n$ £MF per phase 

/o ■ f? Carreat /agg/ng or /eaa'/ag 



Fi B . 6 



coils, to hold any per cent, leading or lagging 
current that may be desired to meet the 
requirements for which the motors have 
been designed. 



COMMERCIAL ELECTRICAL TESTING 



17 



Several installations of power factor regu- 
i have been made in cases where syn- 
chronous motors are used for driving railway 
generators on which the load is subject to 
violent fluctuations, [n such a case withoul 
lator, the sudden changes in load would 
produce a very bad power factor on the line 
supplying the motor . Fig. 5 shows a i ypical ba- 
il i his kind. Here the n gulator is 
designed with six relays which operate on two 
4") kw. exciters supplying excitation currenl fi ir 
two 1000 kw. synchronous motors drivint 

: llations of this kind are 
generally found to require a leading current 
with a power factor ot 80 percent-, and 
this is tli ator is se1 fi ir this 



figure, with a safety device adjusted so that 
the excitation current is held to a certain 
termined amount, upon 

whether the fields are designed for 12."). '_'.">(l 
or other voltage. These regulators, like the 
egulators, are designed to operate 
over a range of exciting potential of 100 
percent, from minimum to maximum, and if 
thi vnchronous motor is properly supplied 
from t he line, the ran; poten- 
tial will be well within these limits. A motor 
should not re. eater excitatii >n than a 
standard alternating current generator, and 
it is to prevent a possible' excess ol exciti 
and consequent injury to motors that the 
limiting device is used. 



COMMERCIAL ELECTRICAL TESTING 

Part III 
By E. F. Collins 

i] \t of Testing Department 



Heating Tests 

The test to determine the heating ol a 
machine is a very importanl and great 

ii taken to obtain reliable temper- 
Any large machine requiring a con 
siderable amount of floor space should have 
the emperatures taken at four diffei 

ent points nearby, and at a sufficient distance 
away from the machine to he unaffected by 
heat from the latter. Two thennometi 
one in air and one in a specially designed 
metal cup containing oil. are used at each 
point to measure the room temperature. 
Before starting a heat run. th ters 

should iced on all important accessible 

try parts, such as series and shunt 
d spools, pole tips, frame, etc.. in the case 
ol a direct current machini In addition, 
tli, n rs should be placed bel ween 

po] r the tempei ature of the 

air thrown of] iron, th.' surface oi the arma 
tun "in the air duets. Each ther- 

mometer should 1" 'I wit h the liulb 

in ci ith the pari of which the tempi 

ature is required, the bulbs being covi 

with putty. Thermometers which are to 

air duets should 
the I .ill ! make 

with the iron lamina hile the 

machine is runnii 

The tlOUld lie shielded from 

currents ol air coming from adjacent pulli 
and belts. Unreliabli -ire 

obtained when the mat him is loi a 

it another machine blows iir upon it. 



A very slight current of air will cause greal 
discrepancies in heating consequently either 

a suitable canvas screen should l.e used to 
shield the machine under test, or the machine 
Causing the draught should lie shut down 

Overload heal runs require considerable 

attention. Where an overload is applied 
tor one or two hours, it should b 
that normal load temperatures have been 
reached before applying thi overload. The 
overload must lie carried only for the specified 
time, since, in many cases, the temperature 
rises rapidly throughout the whole period ol 

t he overload. HclH'c lell^thi'lll' 

ing the' overload period a tew minuti 

make several di grees difference in 

temperatures ol, tamed To avoid con 
tinuing an overload run lor a longer tune 
than that specified, arra its for a 

lent number ol thermometer and resist- 

measurements must be made well in 

advance of the end of the run 

During the heal run all conditions should 
in normal, and the machi lid 1>< 

idly for an) undue heati 
bearings or held spools, or for the ap] 
ance ts. Th. wiring, holding 

holts, belt lace 

In maki ts two methods 

may ' >• tual loa 

lent I nt meat 

obtaining actual 1- may he cmpl 

i as " w. 
ing ba< I aid " induc- 

tion 



18 



CEXERAL ELECTRIC REVIEW 



The "water box" method, as the name 
implies, consists in driving the machine by 
either a motor or engine ami loading it upon 
a "water box," or rheostat. (Fig. 11.) 
This method entails considerable expense. 






jKy-i. to vtitance 







Fig. 11. Connections for Loading a D.C. Generator on a 'Water Box 



since all the power generated is lost. To 
obviate this loss and reduce the cost of test- 
ing, the "feeding back"' method is used 
when possible, especially in the case of large 
d.c. machines and motor generator sets. In 
this method the total machine losses arc 
supplied either mechanically or electrically 
from an external source. In the mechanical 
loss supply method, two machines oi the 
same size and voltage are belted or direct 
connected together and driven by a third 
machine large enough to carry the losses of 
the set. Connections are made as shown in 
Fig. 12. If the machines have series fields, 
these should be connected to boost one 
another. Moth machines should then be 
started up as generators and thrown together 
by closing the switch between them when 
the voltage across this switch is zero. The 
field of the machine that is to act as motor 
should then be weakened, which operation 
throws load on both machines. The speed is 
held constant by the loss supply motor. 
After running at the proper load for the 
specified time, temperatures should be 
taken and tests finished according to stand 
ard requirements. 

If the machines are motors, the same con 
nections should be made and the machines 
thrown together as before. The voltage of 
the system must be held by the i 
running as generator. The only correct way 
of obtaining load is by changing thi speed 
of the set, the brushes having previously 
been set in the running position. Usually the 
speed will have to be decreased, and the 
difference between full load and no 1. 
speed will be the normal drop m speed for 
the motors. Cases sometimes occur where 
tit. of the motor, due to armal 

reaction, increases with increase of load. In 



pumping back, this condition is shown by 
the motors taking an overload at no load 
speed, in which case the speed of the loss 
supply must be increased. 

In the method of electrical loss supply, 
two machines are direct connected 
or belted together and the losses sup- 
plied electrically. Should two shunt 
motors be tested by this method, one 
machine should be run at normal 
voltage, current, speed and full field; 
the other motor to be run as a gen 
erator with a little higher current 
and slightly stronger field than for 
normal conditions. The fields of the 
generator may have to be connected 
in multiple. Connections should 
be made as in Fig. 13. The motor should be 
started first from the electrical loss supply 
circuit and its brushes shifted for commuta- 
tion and speed. After exciting the field of 
lie generator and adjusting the voltage 
between the machines to zero, the circuit is 
closed. The machines are loaded by increas- 
ing the field current of the generator. Care 
should always be exercised when shifting 
the brushes while the machines are under 
load, since a slight change in shift will at 
once change the load. After the heat run 
has been finished and all motor readings 
taken, tlie wiring should be changed and 
motor readings taken on the machine which 
ran as a generator. 

When compound wound generators are 
being tested by this method the series field 
of the motor must be included or the load 
will be unstable. 

Another method of "feeding back," often 
used, is to teed the entire load back on the 




■— oH»tB10BB' — f-^ "OOOOOB060V. 



Fig. 12. Connections for Mechanical Loss Supply Pump Back 

main supply circuit from which the motor 
is run that drives the generator under 
If the main supply circuit is likely to 
vary in voltage, it may be necessary to insert 
resistances between the generator and supply. 
It sometimes happens that the 
voltage oi the generator is below thai of 



COMMERCIAL LI.KCTR1CAL TESTIXC, 



I '.i 



the supply. As changing the line resistances 
will have n< i effed al no-loa c generat* >r 

voltage must be increased until it is e<|ual 
to that of the main supply circuit. Having 
previously calculated the full-load field cur- 
rent from the no-load current and the rati" 
of compounding voltages, the machines are 
thrown together and full load put 
on the gencrai"i' by cutting out the rf^ 

variable resistance. v 

Two similar motor generator sets 
can be tested very readily by the 
"feeding back"' method. As an 
illustration, suppi >se each set consists 
of an induction motor anil a d.C. 
generator. In this case connections 
are made as in Fig. 1 1. The a.c. 
and d.c. ends of the sets are respec- 
tively connected together, one set 
being run normally, and the other 
inverted. The induction generator 
feeds back on the induction motor, 
both taking their exciting current from the 
alternator (A) which supplies the losses. The 
sets are started one at a time from the a.c end, 
and the d.c. ends paralleled by means of a 
voltmeter across switch P. The d.c. motor 
field is weakened until the ammeter in the 
d.c. line indicates that normal current is 
flowing. The weakening of the motor field 
allows the speed of the inverted set to increase 
just enough to load the induction generator, 
while it also decreases the counter e.m.f. of 
the motor a sufficient amount to allow full 
load current to flow in the d.c. circuit. This 
load must be closely watched, as it is un- 
stable. Load ^instability is a rather common 
occurrence in "feeding back," due to either 
variations in shop voltage or speed. 



the armature of a separately excited Looster 
may be connected in series with the armatures 
of the two machines being tested. The 
machines, connected so that they run at 
the same speed, are broughl up to normal 
speed by means of the motor supplying the 
losses. The connecting switch is then closed 





Fig. 13. Connections for Electrical Loss Supply Pump Back 

It will be noted in the "feeding back" 

tests described, that it is necessary to 

iken or strengthen one oi the field to 

iin the load. To conduce the tesl with 

ih.' same field excitation on 1. th machines 



Fig. 14. Connections for Induction Motor Generator Set Pump Back 



and the booster held strengthened until 
normal current flows in the armature circuit, 
the field current being adjusted to give the 
same excitation on both fields. The voltage 
is held across the motor terminals by varying 
the speed of the loss supply motor. This 
method, known as the circulating method, 
is used particularly in the testing of series 
or railway motors. In the latter case the 
machines are geared to the same shaft. 

Another method known as "shifting the 

phase" is used in testing two similar alter 

nators or frequency changer sets. Two 

similar alternators may be direct connected 

by means of a coupling and driven by a 

motor to supply the losses. For example, 

let a three-phase machine be considered, 

the phases of which arc shown diagram- 

matically in fig 15. The machines should 

be run at normal speed, the fields connected 

in series and separately excited to a value 

corresponding to the load at which it is 

desired to make the test . The value of t he 

citation should be calculated from the 
saturation and synchronous impedance 

curves. With phases A and A' conic 
together, the voltage across phases b and !>' 
is read, the eireim closed, and i lie valu 
i 1m current flowing i ibserved. Km <\\ ing the 
volt ,ii letween phases a and b, a' and b' 
and b and b' I he ancle i .1 phase displ I 
may be readily obtained. Should the result- 
mature current b 
or less than that desired, a further trial will 

be ii' 



20 



GENERAL ELECTRIC REVIEW 



The current value will vary nearly as the 
angle of displacement, so that an approxi- 
mate value of the angle desired can be found 
from the value of current and angle previ- 
ously ascertained. When the value of this 
angle has been ascertained, the phase dis- 
placement should be changed, so as to obtain 



a'a 





Fig. 15. Shifting of Phases Shown Diagrammatical^ 

as closely as possible the desired value oi 
current. With the machines still connected 
together as they were originally, the angle 
of phase displacement previously found will 
be increased 120 electrical degrees by con- 
necting a' b. If a' c are connected, a still 
further displacement of 120 degrees is obtain 
ed. If with any of these connections, the 

field of one machine be reversed, a still 
further displacement of 180 degrees is made. 
With the connection which gives the nearesl 
value of armature current to that required, 
a further adjustment may be made by 
shimming the stator oi one or both machines 
up on one side and taking slums out on the 
other side. Tin- circuits should then be 
closed and the heal run made for the sped 
time. Even with the angles o( phase dis- 
placement possible with the various com- 
binations of connections and field rheostats 
it may not be practicable to gel the desired 
armature current. In this case, unbolt the 
coupling and shift the rotor of one machine 
around one or more bolt holes. The "cut 
and try" operations should then be repeated. 

Although the method employed in this 
test may seem long and tedious, the results 
obtained are very satisfai ■ specially 

where it is necessary to make an actual full 
load t< s 

The induction generator methi I is 
times employed in making lull load tests on 



induction motors. Two similar induction 
motors are belted together and run in parallel 
from the same alternator which supplies 
the losses. (Fig. lli.i In order to get full 
load on both machines, the diameter of the 
pulleys must differ by a percentage equal to 
double the full load per cent. slip. 

In starting, the switches A are closed 
and the motor M allowed to come up 
to speed, until the speed of the motor 
running as a generator is above syn- 
chronism. The alternator field is opened 
momentarily, whilst the switches B are 
, closed. The circuit in the alternator 
held is then closed again, and full load 
current flows through the two machines. 
No changes in load can be made without 
changing the pulley ratio and it is 
absolutely necessary that this raiio be 
correct in order to obtain full load. 

Equivalent Load Tests 

Wry often it is found impossible to 

run actual load tests, especially on Large 
machines, on account of limited facili- 
ties. Equivalent load tests have con- 
sequently been devised in which the heating 
ol the machine at a certain load may he very 
closely ascertained without actually loading 
it. One of five different methods may he 
employed in making such a test; viz., "open 
circuit," "short circuit" and "low voltage 
test." "circulating open delta" or "phase 
< il." 
Dired current machines can he sat' 
torily tested by short circuiting the armature 

Upon itself, or through the series field, so 

connected that it will not build up as a series 
ator. The shunt held is separately 
ed from an external source, until Un- 
required current flows through the armature, 
or armature and series field. Tins method is 
excellent for baking and settling the 
mutator. Amperes armature and field, and 
volts field should he read throughout the run. 
In the i alternators, the machine is 

run open circuited, with a field current that 
gives a predetermined percentage over normal 
The run should he continued until 
the rise in temperatures ahove the room 
temperature is constant, after which the 
ine is shut down and the final temper 1 
atures taken. The armature is then short 
circuited, tin- machine started again 
sufficient excitation applied to give a current 
in the armature of a certain pi over 

normal This run should also he continued 
until the rise in temperatures above that ol 



COMMERCIAL ELECTRICAL TESTING 



•21 



the room is constant, after winch the final 
temperatures are taken. The resistance oi 
the field should be carefully measured before 

and after the open circuited run, that of the 
armature before and after the short circuited 
run. and the temperatures of the windings 
cold should also be recorded. During both 
runs volts and amperes field and speed should 
be recorded. During the open circuit run, 
volts armature are recorded, and during the 
shorl circuit run amperes armature. 

On some of the large induction motors, only 

about one-fourth of the normal voltage is 

impressed. The machine is then loaded until 

t lit desired current flows in the stator, the run 

coiit miied as described ab( ive. 

Another method of making an equivalent 
load tes-1 . used especially with turbo and other 
large three phase alternators, is known as the 
circulating open delta run. The phases ol 
the machine are connected in delta, one ■-. i ■ I > ■ 
of which is left open. The fields are excited 
to give the load desired, this excitation being 
determined from the saturation and synchro- 
nous impedance curves. Due to harmonics 
which may exist in the legs of the delta, an 
alternating cross current may flow in the 
winding. Tins is measured by an a.c. am- 
meter (with current transformer, if necessary) 
inserted in the opening of the delta. The 
difference between the square of this current 
and the square of the current with which it is 
desired to load the machine is found, and a 
direct current of a value equal to the square- 
root of this difference is circulated through 
the winding. The run is then continued, a 
careful record of volts armature, direct and 
alternating amperes armature, volts and 
amperes field being made It will be noted 
thai the alternating cross current in one side 
of the right angled triangle and the direct 
current in the other are combined vectorially 
to obtain the load current desired. 

Another method of loading an a.c. gener- 
ator is to give it normal excitation and run 
an unloaded synchronous motor from its 
armature circuit. The field of the motor is 
varied to give a leading or lagging current in 
the armature circuit. This is known as the 
phase control method. The rise in temper- 
ature on the fields during open circuit run, 
and on the armature during the short circuit 
run. is practically the same as will obtain 
during operation under load. Tin- rises in 
tempera in re obtained from a circulat ing <>]» n 
delta run are also so considered. 

With induction motors, it has been found 
that the temperatures on low voltage runs 



when combined with temperatures ai no load 
and normal voltage, give very nearly the 
same results as an actual load test. 

Except in the case of commutating pole 
machines, it is often necessary to shift the 
brushes to get good commutation while under 
load. The point at which the best commuta- 
tion is obtained is known as the running 
point. Its position should be plainly marked 
on both the rocker arm ami the frame by 
means of a chisel. 

A 7oAltfirmtor 




Fig. 16. Full Load Test on Induction Motors 

It is the present practice to adjust all series 
field shunts cold, except in cases where a hot 
compound is expressly desired. This com- 
pounding consists in placing a shunt across 
the series field terminals, in order to obtain 
the proper voltage at no load ami full load. 
The contacts of the shunt should be perfect. 
In making a no-load field setting on the 
machine, the voltage should be raised aboul 
15 per cent, above normal no-load voltage. 
and then reduced to normal. With the 
rheostat left in this position, the load is 
thrown on. and if the compounding is high, 
the resistance of the german silver shun I 
should be reduced, a new no-load reading 
taken, and the operation repeated. This 
should be continued until the machine com- 
pounds according to specifications. 

To take final temperatures after a heat run 
requires the greatest care. Arrangements 
should be made so that no delay results in 
placing the thermometers on the proper par's 
Temperature readings should lie made i 
few minutes until all temperatures begin to 
drop, when the thermometers may be removed 
When final temperatures are being taken the 
hoi resistance oi the machine should In- 
measured. After all the necessary tests 
an- made, the wiring should be removed and 
the high potential tests applied while the 
machine is si ill warm. 

In calculating the rise ol temperature by 
resistance the following formula is used. 



22 



GENERAL ELECTRIC REVIEW 



Let Rt 2 = hot resistance of copper measured 
at the temperature t 2 
Rt l = cold resistance of copper measured 

at temperature /, 
R„ = resistance of copper at 0° C. 

^(^'')|- 23S 

Winn using this formula it is assumed that 
0.0042 is the temperature coefficient of copper 
at 0° C. The rise obtained from this formula 
should be corrected by one-half of one per cent. 
for each degree C. that the final room tempera- 
ture differs from 25° C . This correction is added 
if the temperature is below 25° C. and sub- 
tracted if above. The temperature of the 
winding itself must therefore be very carefully 
observed, as well as that of the room, when 
the hot and cold resistances are taken 

It is often necessary to make a heat run 
on an a.c. machine at a specified power factor. 
To do this, in the case of a generator, the 
machine is loaded on water boxes connected 
in parallel with a synchronous motor. The 
motor merely floats on the line, its field being 
adjusted to give the desired power factor. 
Instead of loading the generator on water 
boxes, the motor is often belt or direct con- 
nected to a d.c. generator which feeds back 
onto the shop circuit. 

Synchronous motors are run under load at a 
certain power factor by being driven from an 
a.c. source of power and loaded on a d.c. 
generator. When power factor runs are made, 
generators should always be run with lagging 
and synchronous motors with leading current, 
unless otherwise specified. 

In addition to an ammeter and voltmeter, 
wattmeters should always be inserted in the 
armature circuit of the machine tested, in 
order to check up the power factor of the 
circuit. 

Equivalent load heat runs are frequently 
made at a given power fan or. In the case of 
an open circuit run, the excitation given the 
machine is a certain percentage over that 
which will give the desired voltage at the 
desind power tart.. rand load. This excitation 
is determined from saturation and synchro- 
nous impedance curves. Short circuit runs 
are made with a certain percentage of exci- 
tation over that required to give the desired 
kilovoh -ampere reading. 

Circulating open delta runs are made as 
previ. lusly described, an allowance being made 
for the proper excitation and armature current 
at the power factor desired. 

(To be Continued) 



HIGH VOLTAGE POWER 
TRANSFORMERS 

By Edwin R. Pearson 

The demand for transformers of greater 
capacities and higher voltages for power 
transmission work has been constantly in- 
creasing for a number of years. Compara- 
tively a few years ago, the construction of a 
transformer of 50 kw., wound for 4,000 volts 
primary, was considered an achievement. 
Later on, a text book on transformers was 
issued showing a transformer of small capac- 
ltv which stepped up to 10,000 volts, and 
the author cited this as an instance of the 
possibility of what could be done. 

From such beginnings advancement has 
steadilv continued so that at the present 





3,750 Kw. Transformer, 138,500 Volts 

time single transformers of a capacin 
from 4,000 kw. up are not at all unusual. 
There are installed on the lines of the Greaj 
Western Power Company, of California, a 



IIK'.H VOLTAGE POWER TRANSFORMERS 



23 



number of 3-phase transformers having a 
capacity of 10,000 kw. each. 

The constanl potential transformer is the 
ing link in every transmission system, 
which fad made it necessary for the design- 
ing engineer to keep pace not only with 
transmission developments but to show his 
ability to produce transformers of a voltage 
in excess of the demand. Voltages have in- 
creased gradually, until a considerable propor 
tion "i Large transmission systems use voltages 
from 90,000 to 1 10,000 The latest advance 
in the art is outlined by the requirements of 
the Stanislaus Power Company, of California, 
the voltage in this case being a long step 
ahead of anything previously used. The 
Stanislaus Company's requirements are for 
:ycle single-phase, water-c< ioled transform- 
ers of :!.7.">U kw. capacity, with a high ten 
sion voltage of 138,500 and a low tension 
voltage of 12,100. 

The high tension windings of the trans- 
formers are so designed that voltages in 
several steps from 40, nun to 120,000 can be 
obtained with transformers connected in 
a"; the maximum voltage of 138,500 
being obtained by "Y" connection. The 
low tension windings are also arranged for 
either 1,000 or 12,000 volts with "delta" 
connections. At all voltages, transform 
will operate at full capacity. 

In designing and building these trans 
formers the standards set for smaller and 
lower voltage transformers have been fully 
maintained. Careful attention was paid to 

ery feature of the design, the proper insu- 
lations, ducts and cooling surfaces being 
ivided to insure uniform strength and 
cooling throughot I all parts. The results of 
the tests show that these efforts were well 
directed, and while there was no fear of the 
outcom i msiderable gratification was felt 
that no sign of weakness was evident through- 
out the 'Sis. An insulation test ol 
double the maximum line voltage; viz., 
280,000 volts, was applied be1 reen thi 
high tension winding and all other parts 
t' ir "in minute 

Inasmuch as these transformers are, as 
above stated, considerably in advance of 
anything else ever attempted, some details 
will doubtless he of intent Efficiencies are 
'.is s. '.is.;. 98.3 and 96.8 to,- mil load, three- 
fourths, one-half and one-quarter loads re- 
spectively. In other words, 'he total losses 
at full load art approximately 1.2 per cent. 
of the rating The non-inducti e regulation 



is approximately L. 25 per cent, at unity p 

factor. 

An idea of the size of these transformers 
and the immense quantity of material re- 
quired is given by the following approximate 




Transformer Removed from Case 



dimensions: Floor space occupied is approx- 
imately 9i ft. by r>\ ft., with a height from 
the floor to the top of the leads oi aboul IT 
ft. Each unit complete with oil weighs L'S 
tons. The windings in each transformer 
require approximately four miles ni . ippei 
strip, built up into the usual flat o 
ture having one turn per layer. The fact 
thai transformers of tins character can be 
built in quantities indicates the enon 
facilities and resources of the manufacturer. 
All of the coils in these transformers are 
impregnated under vacuum with an oil-proof 
insulating compound, making, 
with a good mechanical construction, a 
substantial structure. The leads used in 

transformer^ are the regular oil 
t vpe. wide 

margin oi 



24 GENERAL ELECTRIC REVIEW" 

TRANSMISSION SYSTEM OF THE SOUTHERN POWER COMPANY 

By Johx Listox 



The cotton mills of the Piedmont district 
take about 80 per cent, of the entire output 
of the Southern Power Company's genera- 
ting stations, the balance being utilized in 
various other industries and for lighting. 
The scattered location of the numerous mills 



miles, with a single circuit total of 98-> 
miles. 

The present lines extend north from the 
Rocky Creek power station for a distance 
of more than 100 miles, while their range 
east and west is approximately 165 miles. 



;>*===«< 



_*' 




MAP OTTSANSMiasiCN SYSTEM 
SOTTH* SOUTH L-. 



Fig. 1. Map of Transmission System Showing Existing and Projected Lines 



in North and South Carolina rendered the 
problem of economical transmission un- 
usually complicated, and h was necessary to 
provide several main transmission lines with 
a number of branch circuits and taps to the 
nulls; so that the present transmission system, 
as indicated in Fig. I. involves a network of 
11,000 volt, ll.uoii volt and 100.000 volt, 
three phase, (ill cycle circuits, which havi ai 
aggregate pole and tower length ol 639 



When the new power stations and the pro 
jected hues are completed the total mileage 
of the transmission svstem will be more than 
double that of the existing lines. 

Tin main generating stations at pri 
constructed are arranged for parallel opera- 
tion and arc tied together by means ol a 
trunk line with three circuits, two circuits on 
twin towers and one on poles running from 
the Great Falls and Rocky Creek stations to 



TRANSMISSION SYSTEM OF 



E SOUTHERN I'OWHR COMPANY 



Catawba. The general transmission system 
is not, however, operated as a trunk line, 
but the various sections are interconnected 
through four main switching stations, and 
57 local transformer sub-stations. These 
insure uninterrupted service in case a genera- 
ting stain hi is either overloaded or shul down. 
li trouble occurs on any i tne i >1 I he lines, t he 
particular section affected can be readily 
cut out and the balance ol the line fed 
through the switching stations a1 either 
end. 

The rutin system is patrolled each week, 
fourteen men being employed in this work. 
They keep tl of way clear and <1<> all 

ordinarj repair work; under normal condi- 
tions each man patrols a limited territory, 
but in case ol serious trouble an effective 
communication system enables them to be 
readily assembled within a short time after 
the discovery oi the trouble. 




Fig. 2. Single and Twin Circuit Poles 

At presenl the total transformer capacity 
of the local sub-stations on the 11. nun voll 
lines is 7000 kw., and on thi 1 1,000 voll 
>". :;.")() kw. In the 17 stations on the 
11,000 volt lines the secondaries of the 
transformers are arranged for 550 volts On 

tin il i oil lim t here are 22 statii >ns 

having transformers with 2300 voll sei 

and 8 stations having transformers 
with .V>h vnlt secondaries Nine stations 
are already provided for the 100,000 
-.nit lines, and these all ' irmers 

with L'iiiio vnlt ecom laries In addi 
tion in ' In >e, two stations or the Hhi.imiii 



volt line will have transformers for stepping 
down tn 44,000 volts, for tying in with the 
1 1 nun volt system in case oi breakdown. 

Ai presenl a total ol L30.000 kw. in 
100,000 voll transformers has been installed 
In all sub-stations on the 100,000 volt lines 
three single-phase transformers will be used, 
and m no station will the capacity of the 
transformers lie less than loim kw. 




Fig. 3. Twin Circuit "Aermotor " Towers 
Carrying 44,000 Volt Conductors 



The main switching stations referred to 
above have operators, bu1 mosl ol the local 
transformer sub-stations do no1 require the 
services i if special at tendants. 

At present the transformer connections 
throughout the system are delta delta, from 
generating station through sub-stations to 
the mills. When the 100,000 volt system 
i- [mi in operation, the transformer coi 
nous at the generating station will bechangi 
to delta V. and those at the junctions with 

lln 1 1. 1)11(1 volt line to Y di 

A referenci to Fig 1 and t he following 
i abulatii m will give an idea oi the exti 
territory covered bj the existing lint 
will indicate tin- problems which confronted 
'In engineer "i the Company when planning 
; In n iutes to In- followed, so as to - 

lineal currenl distribution and, ai the 
time, secure immunity 
interruptii i this latter feature 



26 



GENERAL ELECTRIC REVIEW 



being further complicated by the frequent 
local lightning storms which are character- 
istic of the region served. 

For the various transmission lines five 
distinct types of poles and towers have been 
used The two forms of wooden poles shown 
in Fig. 2 were used for the original Catawba 
transmission line — they are either cypress, 
juniper or chestnut (chestnut being finally 
selected as the most suitable available wood), 
and the cross arms are all of hard pine 
creosoted. The twin circuit pole shown on 
the right hand of Fig. 2 is used for 11.000 
volt circuits, while the single circuit poles 
at the left now carry 44,000 volt conductors; 
and will also be used for a short 100,000 
volt line. 

The bulk of the 44. (inn volt lines are now- 
carried on twin circuit structural steel 
" Aermotor" towers similar to that shown in 
Fig. 3, while for the intended 100,000 volt 
lines a 3-arm steel twin circuit "Milliken" 
tower (see Fig. 4) has been provided. These 
towers are practically duplicates of those 
used in the Schaghticoke-Schenectadv line 



of the Schenectady Power Company, which 
were fully described in the May, 1909, Review. 

For running tap fines to mills and earning 
the conductors across railroad tracks and 
through cities, a type of pole similar to that 
used for the Chicago Drainage Power Trans- 
mission system (see Fig. 5) has been adopted. 
These are twin circuit 2-arm poles built of 
structural steel, and are used intermittently 
in the different transmission lines, their 
height varying from 4.5 to 80 feet, the 80 
foot poles weighing 9000 pounds each. 
These poles, as well as all the ''Aermotor" 
type, have their bases weighted with con- 
crete. 

The "Milliken" towers are mounted on 
metal stubs sunk 6 feet in the ground. Where 
the angle of the fine is over 15 degrees, 
however, these stubs are weighted with rock 
and concrete, and where an angle of over 30 
degrees occurs, two and sometimes three 
I >\vers are used for making the turn. The 
weight of the standard "Milliken" tower is 
3080 pounds, and its height from ground 
line to peak .">! feet. The towers are spaced 



EXISTING TRANSMISSION LINES OF THE SOUTHERN POWER COMPANY 











Distance 




Total Mileage 








in Miles 


Circuits 


Single Circuit 






44,000 Volt Lines 


in Operation 
2 


■ > 




Rockv Creek 


Gt. 1 




Aermi 'tor 


4 


Great Falls 


onia 




■ ■ 


63 


2 


126 


Great Falls 


>!I1.| 




Wi »>den 


4 


2 


8 


Great Falls 


Catawba 






36 


1 


36 


Dover 


99 i 




" 


18 


1 


18 


Gastonia 


Kings Mt 




■ * 


L3 


1 


13 


emer City 


Shelby 




■ ■ 


l'ii 


1 


20 


Gastonia 


— Xewton 






32 


1 


32 


( ',as: 


esville 




* ■ 


59 


1 


59 


Catawba 


—Charlotte 




■ * 


18 


2 


36 


Char! 


— Spurries 




" 


12 


1 


12 


Charlotte 


— Concord 






18 


2 




Concord 


-Salisbury 




■ • 


24 


1 


24 


Taps of various mills 






in 


1 


111 






100,000 Volt Lines now Ope 


rating at 44000 Vo 


ts 

2 




Great Falls 


Mi mroe 


Milliken 




74 


Great Falls 


— Chester 




" 


22 


2 


44 


i ter 


nville 






71 


■ > 


1 is 


M nroe 


— Gri 




" 


1 1 15 


2 


210 


High Point 


— Winston — Salem 


Wi ii >den 


17 


1 


17 






* 11.000 Volt L 


nes Total 








W< .oden 


56 


1 


56 



*7 Miles Double Circuit 



'RANSMISSION SYSTEM OF THE SOUTHERN POWER COMPANY 



to average 8 to a mile and a strain tower 
weighing 4250 pounds is used every mile. 
For particularly long spans a special heavy 
lower weighing 6000 pounds is used. 
The circuits arc transposed every 30 
miles. The magnitude of the operations 
carried on by the Southern Power Company 
will be mi Heated by the fact that there are 
2157 of these "Milliken" towers already 
erected, having a total weight of almost 
3700 tons. 

The "Aermotor" towers vary in height 
from 35 to 50 feet, and the circuits are trans- 
posed every in miles. All steel towers were 
assembled on the ground and erected by 
means of gin poles. 

Both copper and aluminum conductors have 
been used in t heconstructionof the line. On the 





Fig. 4. 100,000 Volt " Milliken " Towers with one Circuit Strung 

44,iM)ii volt, 2-circui1 trunk lines, from Greal 
Falls to Catawba, a No. Olio ti wire stranded 
copper cable weighing S tons per mile ol two 
circuits and provided with a hemp core, has 
been used. 



On the 18 mile line between Catawba and 
Charlotte the two single circuit 44,000 volt 
wooden pole lines carry an aluminum cable 
weighing 1029 pounds per mile. This cable 
is b-strand with a cross section of 208,000 



cir. mils. 




Fig. 5. 44.000 Volt Lines entering the Gastonia Substation 



For the 140 miles of 100,000 volt line from 
Great Falls to Greensboro a No. 00 7-strand 
copper cable weighing 2144 pounds per 2- 
circuit mile has been used. 

All conductors except those on the 100,000 
volt lines are carried on triple petticoated 
pin insulators. The center stud provided 
with these insulators is of special design, and 
is the invention of Mr. W. S. Lee, Vice Presi- 
dent and General Manager of the Company; 
it permits the rapid replacement of insulators 
in case of breakage. 

On the 100,000 volt lines multiple disk 
insulators are used — four disks being used to 
suspend each conductor from standard t< 
and ten disks to each conductor on strain 
ti iwers. 

The length of span required on the differ n 
lines varies with the topographical conditions; 
the standard distance for the wooden pole 
lines is 150 feet, the "Aermotor" towers 
being normally spaced 500 feel apart with 
a sag of 5 feet 8 inches. The minimum 
distance between towers is 300 Net, and the 
maximum 720 feet this latter span occurring 
9 here the line crosses Fishing Crick. 

The "Milliken" towers have a stan 
.p. mi oi 600 Eee1 . thi sag at a temperate 
50 degrees F. being 11 feet. A1 a 



28 



CEXERAL ELECTRIC REVIEW 



where the line crosses the Catawba river 
just above the Great Falls station the distance 
between the towers is 1300 feet. The lines 
are strung at an average tension of approx- 
imately 1537 pounds per conductor and a single 
guard wire of -J" stranded Siemens-Martin 




Fig 



6. Bessemer City Transformer Substation Built to 
Accommodate Multigap Lightning Arresters 



steel i- carried along on the peaks of the 
lowers. This guard wire weighs 316 pounds 
per mile, and has a breaking strength of 
9,000 pounds. A similar guard wire of $>" 
steel is used on the wooden pole lines, and the 

"Aermotor" towers are provided with two. 

The sub-stations have the usual equipment 

of transformers, oil switches, switchboards, 

and either multi-gap or electrolytic 

lightning arresters. Disconnecting switches 

are also provided outside each station. 

The interior of a typical substation is shown 
in Figs. 8 and 9, all the apparatus in 
view being of General Electric manufacture. 

Reference has already been mad. to the 
lightning storms which are of frequenl occur- 
rence in the territory through which the 
transmission lines run. and every sub- 
station is. therefore, provided with a light- 
ning arrester outfit. The experience of the 
Company in testing out various types of 
lightning arresters lias resulted in the final 
adoption ol the electrolytic aluminum cell 
type for all future installations, and there are 
already installed 22 sets of this type. 

The illustration, Fi^. 7. shows a Si 
General Electrii electrolytic lightning arfesl 
ers installed outside sub-station and the 
conductors entering the building through 
heavy plate glass windows, and also indicates 
one of the economies which the adoption 



of this type of arrester has made possible. 
When the multi-gap form of lightning arrest- 
er was first used, a high wall was provided 
on one side of the sub-station in order to 
provide sufficient space to suitably install 
them, the type of building used being shown in 
Fig. 6. It was later found advisable to 
discontinue this form of construction and 
erect a separate building in the form of a 
tower similar to that shown in the left hand 
of Fig. 7. in which the multi-gap arresters 
were installed. In view of the great number 
of sub-stations on the system, it is obvious 
that, with the adoption of the electrolytic 
type of lightning arrester, which can be 
installed out of doors, a very considerable 
item in the construction expense of sub 
station buildings has been eliminated. 

The completion of the 100,000 volt lines 
and the construction of the new 100,000 h.p. 
hydro-electric plant at Waterec on which 
work has already been commenced will, at 
an early date, add appreciably to the range 
and volume of the greatest transmission 
system in the South, which is already 




Fig. 7. Highland Park Substation, Charlotte. N. C , Showing 

Old Lightning Arrester Tower on left, G.E. Aluminum Cell 

Lightning Arrester and Horn Gaps in Foreground 



one of the most extensive, in respect to 
aggregate mileage, in the world. 

While the transmission line construction 
work has been characterized by few depar- 
tures from standard practice, a comparison 
of the original 11,000 volt Catawba pole 



TRANSMISSION SYSTEM OF THE SOUTHERN' POWER COMPANY 



29 



line with the 100,000 volt tower system, now 
maring completion, gives a graphic illus- 
tration of the general advancement which 
has been made in transmission Line con- 



Carolina is indicated by the readiness with 
which mill operators have adopted electric 

drive and the very noticeable increase in 
the industrial activity of those sections of 




Fit;. 8. Interior of Kannapolis Substation Showing 

Conductors entering through heavy glass plates 

G.E. K-6 Oil Switch and T.P. Fuses 

struction during the few years which have 
elapsed since the Southern Power Company 
was organized. 

Til- ;uccess with which this Company has 
met the requirements oi the cotton nulls 
and other industries of North and South 




Fiu. 9. Interior of Kannapolis Substation Showii u 

G.E. Transformers, Switches. 

Panels, etc. 

the Piedmonl cotton beh where the trans- 
mission lines of the Sou t hern Power Companj 
have 1 'ecu run. 



30 GENERAL ELECTRIC REVIEW 

GAS-ELECTRIC MOTOR CAR— SELF CONTAINED TYPE 

By A. W. Jones 



The immediate and gratifying success of 
the larger type of gas-electric motor car manu- 
factured by the General Electric Company 
for steam railroads, and the successful 
application of this form of drive on trucks 
passenger vehicles operated on streets 




Fig. 1. Third Avenue Gas-Electric Car 

without rails, has naturally suggested the 
use of the gas-electric drive for cars of 
medium size for which there has already been 
manifested a marked demand. This demand 
will increase and new uses will be found for 
this type of equipment when its reliability 
and ease of operation become better 
known. 

■ The General Electric Company has just 
completed the first car oi this type, which has 
been placed in commercial service with excel- 
lent results. The car is shown in Figs. 1 and 
-. The car body and trucks are especially 
designed for strength and lightness, and the 
equipment, briefly described, consists of a 
direct coupled gas engine and generator with 
citer 'in the same shaft, all completely 
enclosed and mounted between the axles 
of the truck and below the ear floor. 
This arrangement permits low and con- 
venient platforms, and leaves the interior 
of the car entirely unob The 

car is heated in cold weather by hot 
water pipes under th through 

which the circulating water is passed. A 
railway motor, of the is 

mounted on each axle, and the cur 



these motors is transmitted from the generator 
through a controller at either end of the car 
designed to vary the resistance in the shunt 
field of the generator and place the motors 
progressively in series and parallel. The car 
is illuminated by tungsten incandescent 
electric lights, deriving their 
current from the exciter 
circuit. 

The operation is like that 
of an ordinary electric trolley 
car, and. due to the charac- 
teristics of the gas engine 
and generator, there is less 
liability of abusing or over- 
loading the apparatus by 
improper use of the control- 
ler. The car is reversed by 
a reversing handle on the 
controller, without affecting 
the gas engine, and can be 
equally well operated in 
either direction, a controller 
being provided on each 
platform. 

The Gas Engine 

The gas engine is of the 
4-cylinder, 4-cycle type, the 
cylinders being 5| in. diameter by 5 in. 
stroke, and cast en bloc (Fig, 3). The inlet 
and exhaust valves are of large size, located 
on opposite sides and actuated by separate 
cam shafts. The crank shaft is of high grade 
steel, hand forged, and oil treated. Fig. '■'< 
shows a side view of the engine and generator. 
The crank shaft is supported by three babbitt 
lined bearings. Both the crank shaft and 
the bearings have been made of extra large 
size, and much greater strength and bearing 
surface are provided than would ordinarily 
be used on an engine of this size. The crank 
case is arranged so as to provide a constant 
level system of -plash lubrication for the 
engine, oil being kept in circulation and tin- 
level maintained by a centrifugal pump with 
stable overflow. 

The pistons are of the trunk type and made 
of the same material as the cylinders. They 
rovided with four cast iron snap rings. 
The wrist pins are of steel, hardened 
ground, and are fastened in the connecting 
rod in a special manner. 

The connecting rod is of drop forged 
and i il treated. The cylii 
are water jacketed, circulation being secured 






< '.AS-ELECTRIC MOTOR CAR 



31 



on the therm. . siphon principle, the circulating 
water being c<>< .led by a radiator located i m the 
roof of the car. which can beseenin Fig. 1 This 
radiator has a cooling surface of approximati 
lv 900 square feet, ami a capacity, including 
water jackets and piping, of about 65 gallon 

A centrifugal type of governor gear driven 
from the inlet cam shaft is furnished, which 
acts directly on a balanced valve com rolling 
the quantity of the mixture admitted to the 
cylinders, and maintains the speed of the 
engine; and generator with small variations 



The engine exhausts into a muffler, the 
exhaust gases thence being earned to the 
roof of the car. thus avoiding all odor of 
burned gases and eliminating noise. 

Generator and Exciters 

The generator and exciter, Figs. -1 and 5, 
are direct coupled to the gas- engine and 
are completely enclosed. The armatures of 
these two machines arc assembled on the 
shaft so that the commutators are adjacent. 



ick 
da 
. of 
<ler 



hill-climbing 
ui the- " Invincible" Tall, 




■ 

\ 
J 



IS ACERICA ALWAYS AHEAD OF THIS COUNTRY J THE FIRST AUTO -TROLLEY CAR RUN 

IN NEW YORK. 

TbU photograph ot the first auto-troller car run «n 40 experiment in New York suggests the question whether 

America is always io advance ot Great Britain in the matter 0! new inventions, especially in regard to the problem 

ol road locomotion and quick transit in great cities. 



Ion News 



Fie. 2 



at about 800 r.p.m. Ignition is provided by 
a gear-driven Bosch low tension magneto 
and magnel ic plugs. 

The entire engine is so designed thai when 
it is assembled together with the govi 
magnet" . irk plugs, it is completely 

enclosed thus being protected againsl dust, 
dirt and water. This construction is clearly 
shown in Fig. 'i. 

The carbureto the Venturi type, with 

feed, thi gasolene being admitted by 

gravity from tl undei 

tr seats. T\\o ..I 1 h 

each of 35 gallon 



This arrangemenl permits of using but one 
tion cover tor both machines. The 
generator is shunt wound, and the exciter, 
in addition to the shunt winding, has a eri 
field 

Motors 

Two standard GE-60 250 volt rail 
in. iti irs an- used Eai I. motor will de- 
velop 22 h.p., the outpul being based oi 
standard 

Th. 
bolted togethi r, the 



32 



GENERAL ELECTRIC REVIEW 



are hinged, and the lower frame is arranged 
to swing down so as to permit of inspection 
of fields and armature. The axle and arma- 
ture bearings are of bronze, lined with babbitt. 



A separate reversing handle is provided, 
so designed that the controller is locked in 
the off position when the reverse handle is 
removed. 




Fig. 3. 35 40 H.P. Gas Motor Diiect Connected to 15 Kw. 250 Volt Generator 



and are designed for use with oil and waste 
lubrication. 

The pinions and gears are of steel, and 
entirely protected by a gear casing. The 




Fig. 4. Generator and Exciter Armatures Mounted on Same Shaft 

number of n eth in the gear and pinion, that 
is to say. the gear ratio, maj be varied 
suit differem i ■ inditii ms i <i service. 

Controllers 

Two controllers (Type I' r> A are furnish- 
ed, "lie for carli end of tlie car. These con- 
trollers arc provided with the usual reversi 
cylinder, fingers, ami connections for placing 
rogressively in series ami parallel. 
Magnetic blow mit coils for main conta 
ami cut-nut switches for tin- motor, circuits 
are also provided. In addition there 
provided fourteen steps introducing resist- 
ances in the generator shunt field for varying 
the voltage impressed upon the motors, thus 
securing a smooth and even rate nf accelera- 
tion. 



Truck 

The truck is of a special ligb.1 construi 
of riveted plate frame, and is sup] 
the journal boxes by helical springs 

Tlu car body is carried mi the truck by 
means of helical springs, in addition to four 
halt' elliptic springs which prevent excessive 




Fig. 5. Generator Field 

udinal r ar body. The 

truck is 7 t't . li in. wheel base with .'!1 in. 
win ■ 

Tlie generating unit is swung centrally in 
1 1. nlted directly to CTOSS ties 
which are riveted to the side fran 

The motors arc outside hung on the truck, 
with the suspension side supported on the 
main truck frame. An extension sh. 



CAS- ELECTRIC MOTOR CAR 



33 



broughl ou1 from the engine to the end of 
the car for purpose of cranking. 



Car Body 

Tile car body, which is clearly 
Fig. 1, is designed with especial re 
strength and lightness. The 
platforms arc semi-vestibuled. 

Tin- roof lias no monitor, 
it being (Ionic shaped anil pro- 
vided with suction ventilati >rs 
The radiator is placed on the 

over the center i >f the l^"" 
car, and is connected to the "z,* ™ 
water jackets ol the cylinders ^ 
by pipes enclosed within the % ieo ° 

r posts of the car. The 5 
seats arc longitudinal, finished | 
in rattan, and have a capacity 
of 26 passengers. Trap doors 
arc provided on the bottom of 
the car floor, givingready ac- 
cess to engine, generator and 
motors. The controllers, hand 
brakes, auxiliary switches, etc., 
are carried on the platforms. 
The accompanying table 
gives principal dimensions: 

DIMENSIONS 

Length over bumpers 

Length of car body (inside) 

Length of each platform 

Width over bodv 



shown in 
ference to 



Width ever radiator 8 ft. II in. 

I [eight from rail to top of roof II ft. 1 in. 

Height from rail to top of radiator 12 ft. I in 

An obvious usefulness for this type of car 
on trolley systems lies in its adaptation to 
"owl" trips, thus permitting the power 




/ i 3 4 S 6 7 i 9 10 II IZ 11 14 15 IS 17 IS 19 ZO 
MILES P.' H HOUR 



Fig. 6. Performance Curve of Gas-Electric Car 



28 ft. n in. 

19 ft. ti in. 

4 ft. in. 

7 ft. 4 in. 



station to be entirely shut down, say. between 
midnight and morning, when otherwise one 
generating unit would have to be kept in 
operation. 

The type of car body which may be 
used with this equipment is, of course. 



TABLE OF SCHEDULE SPEEDS IN FREQUENT STOP SERVICE 

AND ON GRADES 



AVBRAGB LENGTH OP RUNS IN MILES 



Per Cent. 
i trade 



Duration of Stops 
.i Sees. 



Duration of Stops 
30 Sees. 



II 


6 7 


9.0 


10.5 


25 


6.5 


8 5 


9.8 


..-,u 


6.3 


8 1 


9 2 


.* .i 


ti. 1 


7 6 


8.6 


; 00 


:, 9 


7.2 


8.0 


1.25 


5.7 


6.8 


7.6 


1.50 


5.5 


6.5 


7.2 


1.75 


;, 3 


6.2 


6.8 


2.00 




5.9 


6 I 



I 1.5 


12.4 


1 1 3 


Ki.7 


1 1.5 


10.5 


9.9 


10.6 


9.7 




9.7 


9.0 


8.5 


8 9 


s 3 


7.9 


8 2 


7.8 


7 1 


7.6 


7.3 


7 n 
i; ' 


7.2 
6 8 


6 8 

6 i 



• 7 


.8 


1 1.9 


12.4 


ll.ii 


l I l 


ln.l 


10.5 


9, I 


9.7 


8.7 


8.9 


VI 


8.3 


i ■> 


7.7 


7.0 


7.2 


6.5 


e 6 



12.9 
I 1.9 
in 9 
10.0 
9.] 
8.5 
7.9 
7.3 
6.7 



i ii 



13.3 
12.3 
11.3 

in.;; 
9.3 
8.7 
8.0 

7 I 
6 s 



j.i) 



15.9 

1 I I 
12.9 
1 1 5 
10.3 
9 5 
8 7 
7 9 



17 I 
15. 6 
13 9 
12.3 
10 8 

9.1 
8.3 

7.1 



Running 



25 1 1 
20.0 

I7.(i 
1 I :. 
13.0 

I 1 :, 

inn 

9 n 

8 5 



34 



GENERAL ELECTRIC REVIEW 



not restricted to that shown in the illus- 
trations and described above. Many other 
designs suggest themselves. A baggage 
space can be provided. An open type 
of car with transverse seats will be useful 



in warm climates. A flat car with plain 
roof to support radiator, and open ends 
and sides will be found very convenient 
in construction work for carrying men and 
tools. 



STANDARDIZATION RULES OF THE A.I.E.E.* 

By Dr C. P. Steinmetz 



The subject on which I desire to speak is 
the Standardization Rules of the American 
Institute of Electrical Engineers. My reason 
for selecting this subject is that, in my 
experience, these standardization rules are 
not as well known to many engineers as their 
importance makes it desirable. In ray 
opinion, the Standardization Rules represent 
the most important work the American 
Institute of Electrical Engineers has ever 
undertaken, and constitute one of the most 
important documents in the literature of the 
electrical engineering industry, for I believe 
that the rapid and successful advance of the 
electrical industry of the United States is to 
no small extent due to their existence. 

At present few of us realize the conditions 
which existed before these rules were drawn 
up and generally adopted. These rules have 
made it possible to build good apparatus 
and sell good apparatus, which procedure was 
not always possible before that time. The 
standard set by the rules is high, but not too 
high. It can easily be attained and yet 
it is sufficiently high to be safe, though no 
more. Since their adoption, the rating of 
any piece of electrical apparatus whatever 
means something definite, and means the 
same thing within the limits of the relative 
conscientiousness of the different manu- 
facturers, no matter from what manufac- 
turer it may be bought; and these limits 
are very narrow, because the tests are 
specified and may be easily made to check up 
the required performance, thus making it 
impossible to deviate much from the standard 
wit In mt having it noticed. Now that has 
not always been the case. On the contrary, 
in the early days, a small manufacturer 
would make high guarantees regarding the 
efficiency and performance of his apparatus 
which an engineer, knowing all about the 
apparatus, could not make. It will be real- 
ized that it was a very severe handicap to 
the advance of the electrical industry that 

• Lecture before Section A I I-'. E , Nov 2, I'.mg 



those engineers w T ho knew as much about 
the apparatus as was known at that time, 
were not able to build as good apparatus as 
possible because it could not be sold in 
competition with inferior apparatus which 
was guaranteed to have higher efficiencies. 
For instance, in those times core loss was a 
quantity not generally known. Quite com- 
monly small manufacturers guaranteed effi- 
ciencies without figuring the core loss. It 
can be realized that a larger manufacturing 
company, having engineers who understood 
and could calculate this, might have built 
apparatus with much lower core loss and 
much higher efficiency, and still could not 
guarantee as high an efficiency as the manu- 
facturer who did not take it into considera- 
tion. They knew of losses which others did 
not and which others therefore did not 
consider. At that time the commutator 
losses had just begun to be found out. but 
often the manufacturer did not dare include 
them in the losses because nobody else did, 
although they amounted to several pier cent. 
It was a very unfortunate condition of affairs 
which made it necessary for those designing 
engineers who knew of the losses in the ap- 
paratus to count them in, while the engineers 
who were ignorant of their existence were 
able to sell inferior apparatus under higher 
guarantees; tor the happy custom used to 
count only those losses which were specified, 
and of course the less specified the less the 
losses appeared. That condition of affairs 
has passed, and now the higher class of 
producers find it desirable to have everything 
known; to have tests ol the performance and 
calculation of efficiency made, and the 
customer to know what the efficiency is, 
because they can gain by it. The same 
advantages accrue to the customer. He 
was formerly helpless when in the market 
to buy electrical apparatus, as one manu- 
facturer guaranteed his apparatus at 92 per 
cent, efficiencv while another anil smaller 



STANDARDIZATION RULES OF THE A.I.E.E. 



35 



manufacturer was willing to sell him the same 
kind of apparatus cheaper and guaranteed at 
95 per cent, efficiency. What could the 
customer know and do? That condition 
is not possible now. for the manufacturer 
could not guarantee efficiencies not in exist- 
ence — he would be found out. In 1S92, 
when I wrote a paper on hysteresis losses, 
I remember that one engineer even claimed 
there was no such thing. It could not be, 
because the efficiency was known. There 
could not be such a loss, because it would 
have shown up in the efficiency and it would 
have been notice 1. All that has now become 
generally known and understood, and this 
fact is to a very large extent due to the 
educational work done by these standard- 
ization rules. 

The benefit resulting from these rules 
extends throughout the entire held of elec- 
trical work. In those early days, it must be 
realized that it was not generally accepted 
and recognized that the efficiency could be 
got by adding the losses. Commonly tin- 
engineers or customers rejected an efficiency 
test made in this manner. The recogni- 
tion of the correctness of the method of 
measuring efficiency by adding the losses 
has from the first been 1 .fought out in those 
Standardization Rules. I recall an instance 
where some big machines were built and the 
question was. how to measure their efficiency. 
The input and output could not be measured 
very well on a 400 kw. machine, which, in 
those days, was a monstrous machine. It 
was agreed that the core loss was one of the 
losses which was to be added. The customer 
insisted that it be taken at no load and full 
load excitation. The machine was one of 
those early high frequency alternators, and 
when run light at full load excitation gave 40 
or 50 per cent, higher voltage and two or three 
times the actual core loss obtained at full 
load. It took a long time to satisfy the 
customer that the addition of the losses 
gave the correct efricii d v. Ultimately, 
however, the machines were accepted. When 
these machines went to England and were 
turned over to the customer, he would not 
accept them without further test; so they 
were coupled together, oni being used as a 
motor and the other as a generator, and a 
whole series of tests were made, measuring 
the power input and output, and the input 
at all possible displacements, etc., to satisfy 
him that the efficiency was right. He finally 
accepted those tests, although I do not 



but hr gol 



believe they meant anything; 
what he wanted. 

We know now what the efficiency is, what 
the losses are, and how the efficiency should 
Ik- determined. Some consulting engineers 
had the habit of drawing up the most wonder- 
ful specifications, often 65 pages or more, 
specifying everything covering the armature, 
conductors and main- other things. This 
was entirely improper, because that was no 
business of the customer what In- looks for 
is the performance. Even prominent con- 
sulting engineers frequently specified things 
of decided disadvantage and made it im- 
possible to get the best machines for their 
purpose; for, while desiring to get the best 
apparatus, they made the mistake of specify- 
ing things which would be a disadvantage, 
as they were not familiar with the state of 
the art at that time. The early days of the 
industry are full of such instances. 

Even though an agreement was reached, 
nothing definite was understood it meant 
a different thing to different people. Speak- 
ing of the regulation of a machine: what 
did it mean? The Westinghouse Company 
understood something entirely different when 
guaranteeing regulation from what the Stan- 
ley Company or General Electric Company 
did. The one understood the percenta 
rise of excitation from no load to full load, 
and the other, the percentage increase of 
voltage at full load excitation when full load 
is thrown off. Such disagreements naturally 
made matters very difficult for a customer 
desiring to get apparatus, for the regulation 
would be guaranteed by one manufacturer 
as 8 per cent, and by another as 12 per cent. 
Twelve per cent, might have been a better 
regulation than 8 per cent, because the 
latter might mean that if load is thrown off 
at full load, the voltage will not rise more 
than <S per cent., and the other, if a change is 
made from no load to full load, a hill excita- 
tion ol 12 per cent, increase was necessary. 

Before people could understand each other 
and before customers could compare intelli- 
gently the offerings of different mamilaet uivrs, 
it became necessary to have some definite 
meaning for the different terms. People 
mi -lit use the same term and mean very -I 
erent things. 

The radical advance in the industry became 
possible only when all these childn n ises 

the competition of manufacl urers ol inferior 

apparatus guaranteeing superior results by 
reason of lack of knowl ., becaim 



36 



GENERAL ELECTRIC REVIEW 



eliminated, and all manufacturers and cus- 
tomers could meet on a common footing, 
employing the same terms and having to 
come up to the same performance. So in 
those early days the question of standardi- 
zation was really of the greatest importance 
to customers, operating engineers, and to 
the manufacturers; and it was natural that 
the question of establishing standard rules 
should be brought before the Institute. That 
this was done is due to Mr. S. D. Greene, who 
is still a member of the organization. Mr. 
Greene read a paper before the American 
Institute of Electrical Engineers, drawing 
attention to the necessity of deciding what 
represented the best standards, the besl 
practice, and the best definitions in the 
field of electrical engineering, as far as the 
prominent engineers could agree on the 
subject. As a result, the motion was made 
and finally carried to establish such stand- 
ardization rules, and a committee was 
appointed to draw them up. Naturally, 
there was considerable discussion as to 
whether such rules would not handicap the 
development of the industry; they might 
hinder it, because of limitations, or they 
might sap inventive activity by establish- 
ing standards. Experience has shown that 
this has not been so. The rules have been 
very helpful in assisting development, have 
made unnecessary an enormous amount of 
waste effort, have combated foolish ideas 
by educating people to understand the 
meaning of terms, and have cleared up 
mistakes of understanding and made it 
possible for the results of the work to be 
recognized. If machinery and apparatus is 
superior it can be shown which advantage 
was not always possible before. It is amus- 
ing now to remember some of those discus- 
sions. For instance, a motion was made 
that engineers connected with manufacturing 
companies should not be included in this 
Standardization Committee because of the 
fear that they might make the standard of 
the rules so low that it would be easy to 
build apparatus. As a matter of fact, most 
of the work on the rules as they stand has 
been done by Mr. C. F. Scott, of the Westing- 
house Company, and by myself, both repre- 
senting manufacturing companies which have 
always insisted on strictness and rigidity, and 
on making the requirements as high as 
could well be made, firmly resisting any 
attempt to reduce them. This is natural, 
because it can easily be seen that the manu- 



facturer has no objection to building better 
machinery — it is really an advantage, because 
the better machinery will give a better 
record and not as much trouble; while if a 
cheap and poor machine is built the manu- 
facturer gets the blame for it. and justly. 

The standardization rules are of great 
advantage to the producer, to the designing 
engineer, and to the customer. They were 
started by a committee appointed by the 
A.I.E.E. and since then a committee for 
this work has been appointed every year, 
Every few years it becomes necessary to 
bring the rules up to standard and to add 
whatever new features have been developed 
in new industries that require attention. 

Standardization rules have been drawn up 
and an attempt made to follow them in 
other countries, but in no country, as far 
as I know, have they been so generally 
accepted and so helpful to the industry as 
here in the United States. To a very large 
extent this is due to the close co-operation 
of the manufacturers, operating engineers-, 
and theoretical men here; but in other 
countries the tendency is to delegate it to 
the theoretical men, who draw up rules from 
mere theoretical knowledge, which no manu- 
facturer or customer can follow or cares to 
follow, and therefore such standardization 
rules have occasionally been handicaps. 

It is natural that manufacturers' engineers 
should have done most of the work in draw- 
ing up the rules, because the engineer who 
designs the machine, and afterwards follows 
it in test and is held responsible by the 
Commercial Department for its successful 
operation, naturally knows the ins and outs 
n| the machine better than can anyone else. 
He therefore knows better to what extent 
strid specifications should be made in order 
to gel the best machine; and lor him it is an 
advantage to see that specifications are high 
enough, so that he may not be held respon- 
sible t>ir troubles that develop in his produc- 
t ion i iutside. 

The reason that the Standardization Rules 
have been so successful is that, from the 
beginning, the principle has been very 
rigidly maintained that the performance 
should be specified and not the design data. 
For instance, in an armature winding, it is 
proper to specify the temperature, but it 
would be improper to specify curren. density. 
Any specifications or standards of design 
data are a handicap to the development of 
the industry; but the standardization of 



STANDARDIZATION RULES OF THE A.I.E.E. 



37 



performance has put a premium on designs 
which will make it possible to produce the 
same performance with a less amount of 
material and smaller apparatus, thus making 
the apparatus cheaper to manufacture. 

Another mistake which has been carefully 
avoided, and which has been made especially 
by our European friends, is the attempt to 
specify size, speeds, etc. Such specifications 
tend to stop the advance of the art. 

As I have already stated, the result has 
been accomplished by the co-operation of all 
entatives of the electrical industries 
in the country, and therefore the rules have 
nut met with much difficulty in finding 
general acceptance. 

We now come to a more specific discussion 
of some of the leading features of the Stand- 
ardization Rules: — 

Classification of Apparatus. Classifying 
apparatus as motors and generators was 
entirely unsuitable. If it is desired to classify 
and draw up rules for measuring efficiency 
and specify what performance should be 
expected from motors, it is evident that 
synchronous motors, direct current shunt 
motors, induction motors and railway motors 
cannot be put in the same group. They are 
entirely different types of apparatus. Neither 
can synchronous generators, direct current 
commutation generators, and induction gen- 
erators be put in the same group. Again, a 
direct current generator and direct current 
motor are practically the same machine. A 
direct current motor can be run as a generator, 
and inversely, a direct current generator 
can be run as a motor. A synchronous motor 
and an alternating current generator are the 
same class and type of machine, and the 
specifications for the performance of each 
would be the same. There may be some 
quantitative differences of a minor nature, 
as for instance, if a synchronous machine is 
designed to operate only as a motor, a higher 
armature reactance is chosen than if the 
machine is designed to operate only as a 
generator. We also have compound motors 
and shunt generators, and a definite line 
cannot be drawn between generators and 
motors; but there is a distinct dividing line 
between commutating machines and syn- 
chronous machines and between induction 
motors and synchronous motors. In many 
cases machines are installed where it is 
iMe it, say whether they an- generators 
or motors. To-day they may In- running a 
synchronous motors and torn* row as gen 



erators. It is common in steam stations or 
water power plants to install synchronous 
motors to receive power from the trans- 
mission line and drive other apparatus, such 
as commutating machines for railway work, 
etc. During a period of low water it may 
not be possible to get power enough from tin- 
water and the synchronous motor has to 
be started as an alternating current generator. 
That is a very common thing. It became 
necessary to find a classification of electrical 
apparatus based on its nature, structure, 
and construction, and not on the particular 
use to which it happens to be put. 

As an illustration of the confusion which 
existed in nomenclature of electrical apparatus 
before these rules were generally accepted, 
I mention the converter and transformer. 
It just happened that when the Westing- 
house Company started to build alternating 
current transformers they called them con- 
verters. When the Thomson -Houston Com- 
pany, the predecessor of the General Electric 
Company, started to build transformers, 
they called them transformers; so the same 
type of apparatus went by the name of 
converter in the Westinghouse Company 
and transformer in the the General Electric 
Company. A synchronous converter was 
developed by the Westinghouse Company 
which they called a rotary transformer, 
because the stationary apparatus was called 
a converter; and the General Electric Com- 
pany, which had used the name transformer 
for stationary apparatus, naturally called 
the other a rotary converter. This is one 
illustration of the different definitions which 
weie applied to the same things. The 
Standardization Rules adopted what appeared 
to be the best practice, and in this case 
adopted the name transformer because it 
had come into general use by other people. 
Rules were drawn up to establish as defini- 
tions those terms which appeared to the 
committee as representing the best practice 
and were most generally accepted . Then we 
find definitions of quantities like load factor, 
saturation factor, pulsation, etc., which had 
to be standardized so as to mean something 
definite. 

With the advance of the art, this work 
has been expanded and new chapters in- 
serted. The procedure which has I 
followed is never to standardize anything 
until best practice has already crystalized 
upi .n ome definite form, and not to ( 
definitions, but accepl tl lefinitions 



::s 



GENERAL ELECTRIC REVIEW 



toward which good practice tends and which 
therefore can easily be accepted. It is no 
longer the definition of a competitive company, 
but a definition of the Institute, an im- 
partial body. A company may hesitate to 
change the name of its apparatus and adopt 
the name used by a competitor, but there 
can be no hesitation to adopt the name 
given to it by the general body of the Insti- 
tute; and this tends to uniformity, which is 
not only desirable but absolutely neces- 
sary. 

Then comes the second part of the rules, 
covering specifications of performance of 

apparatus, and tests; that is. how the ap- 
paratus should perform and how this per- 
formance should be determined by test. 
It can be readily appreciated that one of the 
most important considerations is efficiency 
the definition and determination of efficiency 
— and one of the most important features of 
the work done by the rules is the establish- 
ment of a method of measuring efficiency by 
adding the losses, making that method safe 
by carefully scrutinizing the losses and 
showing how they should be measured. 
These efficiency specifications and the method 
of making tests are well worth cartful study, 
because they are really the general standard 
for testing electrical apparatus. 

In the matter of insulation, which is an 
important one. attention is directed to the 
importance of high voltage tests and the 
relative unimportance of measuring the ohmic 
resistance of insulation. The ohmic resistance 
of the insulation is increased by baking, and 
in this way one could get 50 megohms or 
more; but this is liable to weaken the dielec- 
tric strength ol the insulation. Tests of 
ohmic resistance are desirable as merely 
showing tli.it there is no greal leakage but 
they do not show how the insulation will 
perform, which performance is given by the 
dielectric test. A standard of one minute 
has been established for tests for dielectric 
trength. It is unsafe and objectionable to 
i \ti iid the time of test much longer, because 
of harm to the insulation. High volta ■■ 
- must be made at voltages very much 
higher than those to which the insulation 
will be normally subjected, and such high 
voltage puts a strain on the insulation which 
deteriorates it. Then tore, the test should 
noi be continued longer than necessary to 
make sure that the voltage is there, and one 
minute is sufficiently long for this purpose. 
With some kinds of apparatus, however, a 



half hour is specified. With some apparatus 
half an hour is not so bad, although a minute 
is better. Naturally when saying a minute 
is better, the same test is intended to be 
applied. One minute at 25,000 volts is 
preferable to half an hour at 10,000 volts. 
The shorter the time the voltage is kept on, 
with correspondingly higher voltage used to 
get the same severity, the less will be the 
deterioration of the insulation. Apparatus 
must be tested with at least twice its rated 
voltage twice the rated voltage of the 
circuit to which the apparatus is to be con- 
nected — except, of course, on machines for 
very low voltage, on which tests are made at 
a voltage much higher in proportion. There 
would be no sense in testing a 100 volt ma- 
chine at 200 volts; but when you come to 
10.000 volt apparatus, the test which exper- 
ience has shown is sufficiently high, but not 
too high, is 20,000 volts, which really means 
four times the normal voltage strain. The 
reason that this is necessary is because of 
the abnormal conditions of operation which 
may occur. On a high voltage system, if 
one side of the winding becomes grounded, 
the whole rated potential is exerted between 
the winding and the iron; and in normal 
operation, during conditions which we must 
expect frequently, voltages occur which last 
but for a small fraction of a second that arc 
as high as the testing voltages of the ap- 
paratus. Xo insulating material can stand 
higher voltages momentarily than contin- 
uously. It would not be safe to lower the 
testing voltage. Once it was done. It was 
very difficult to test alternators at double 
voltages. At that time a 20,000 volt alter- 
nator could be built that could be tested at 
30,000 volts, but which would not stand 
io. ooi) volts. Since the engineers agreed 
that it would be desirable to have such 
ernators, they asked the Standardization 
Committee to lower the specification for 
high apparatus to \\ times the rated 

voltage. All kinds of breakdowns follov. 
the introduction of this practice, and we 

le back to the double voltage, and ex; 
nine has shown that the double voltage is 
not to., high and not too severe a test. 

Then going further, overload capacities is 
another point. Very great difficulty existed 
formerly in eon our apparatus with 

make-, and it has often been noticed 
how superior the continental companies are 
in their designs; how much smaller and 
cheaper their smaller motors are; but they 



Rl >SEXBERG GENERATORS 



39 



do not follow tin' Institute rules, and a •"> 
h.p. motor may mean a very differenl thing 
with them from what it dors with us. It may 
■ i tean a motor which can give power at but ."> 
h.p., or it may mean a motor which can con- 
tinuously carry power averaging ■"> h.p.; 
sometimes going below that figure. The 
tendency here in America has been to rate 
the apparatus at the average output which 
it can give. Without any guidance of 
standardization rules, the tendency has been 
very often to rate apparatus at the maximum 
which it can perform. Naturally, where 
, two classes of apparatus are compared, 
tin one appears very much larger and more 
expensive than the other. The uniform 
rating which has been established as a 
minimum is 25 per cent, overload for two 
hours, and for motors or apparatus which 
may go out of service by reason of ex- 
cessive overload. 50 per cent overload for 
one minute. Otic minute means that it 
shall be able to carry oil per cent, overload 
at least, without stopping, falling out of 
Step, or doing anything to interrupt oper- 
ations. 

Now as to temperature rise: The tin form 
rating of oil C. rise by resistance and 40° C 
by thermometer has been established for all 
apparatus, with a few exceptions. Com- 
mutators and brushes are allowed 5° C. 
more. In looking over these specifications 
we must naturally realize that they do not 
attempt to represent best practice, but the 
maximum safe value. It does not mean 
best practice to specify 50° C. : very commonly 
40° C. is called for. In drawing up general 
specifications, it is not safe to permit a rise 
of more than oil C 

I have spoken of Standardization Rules, 
hut really, as they stand at present, they 
constitute a list of all electrical apparatus, 
and very few. if any. kinds of apparatus which 
is used or contemplated m any electric 
light or power system, are nol mentioned, 
described and classified m those rules suffi- 
ciently for an engineer to be able to handle 
them and know what to do with them, and 
specify their performance. In this resped 
they are more complete than any text hook ol 
electrical engineering I know of. for during the 
lasl twelve years so many people have worked 
on them, studied them, and discussed them. 
that they have really become a very com- 
plete compendium or dictionary ot electrical 
apparatus in the matter of it-, performam i 
and test . 



ROSENBERG GENERATORS* 



By 



1-. Hall 



In supplying power for projectors some 
means must be provided whereby a drooping 
characteristic is obtained at the lamp ter- 
minals; ordinarily this is accomplished by 
inserting a resistance in scries with the arc. 
Upon the steepness of the characteristic, or 
rate of change of potential at the lamp 
terminals, with reference to the current, 
depends the regulation of the current. With 
rheostatic regulation the higher the potential 
of the line from which the projector is operated, 
the steeper the characteristic and the closer 
the regulation, as shown by curves in Fig. 2. 

In operating large projectors such as the 
80-inch size, taking an amount of current 
relatively high, it is impossible i" obtain a 
characteristic too steep; in fact, as near actual 
constant current conditions as possible is 
desirable. To meet this latter condition, as 
well as to save the energy ordinarily wasted 
in rheostatic regulation, the Rosenberg type 
of generator seems to be the solution of the 
problem. This type of generator (the Rosen- 
berg American patent rights having been 
purchased by the General Electric Companyl. 
has been described in the Review (December. 




Fig. 1 

1907) and various other technical magazines 
and little can be added to the mass of 
literature already published. 

As constructed a1 the present time il resem- 
bles, to a certain extent, an i irdinary bipolar 
generator, bul differs from it by having four 

sets of brushes. Two iA the lour sets of 
* Reprin tsd from the I) '.itltry 



40 



GENERAL ELECTRIC REVIEW 



brushes are located in the same position on 
the commutator as in the ordinary generator, 
and are connected together, or short circuited, 
by a heavy copper conductor, and are called 
the "short circuit" brushes. The remaining 
two sets of brushes, called the "service" 
brushes, are located midway of, or 90' 
from the short circuit brushes. 

From the field excitation is derived the 
primary flux, which induces a current in the 
armature flowing through the short circuit 
brush circuit, as would be the case in an 
ordinary generator short circuited. The 
short circuit current sets up a secondary flux 
at right angles to the primary flux, the path 
of which is through the armature and pole 
shoes. This secondary flux induces a current 
in the service brush circuit, which in turn 
induces a tertiary flux at right angles to the 
secondary and 180° from the primary flux, 
and having a tendency to neutralize the 
latter. 

The flux distribution is diagrammatically 
shown in Fig. 1 and the relation between 
service and short circuit amperes at different 
generator voltages is shown in Fig. 3. The 
curve sheet also shows the load amperes taken 
by the motor driving the Rosenberg generator. 
This generator was shunt separately excited, 
and it will be noted that the curve showing 
the current in the short circuit brush circuit 
would extend beyond the limits of the curve 
sheet if completed. The operation may 
perhaps be better understood by outlining 
the conditions at no load and the actual 
short circuit of the generator with shunt 
separate excitation. 

At no load the tertiary flux is at zero, as 
no current is being taken from the generator. 
and the excitation due to the primary flux 
will be at the maximum. Under these 
conditions the current in the short circuit :d 
brush circuit will be the maximum, but the 
secondary flux induced by it has little effect 
on the primary flux. 

If tin' generator be short circuited, which 
can be done with impunity, the tertiary flux 
is at its maximum, being induced by the 
service current, and its magnitude is such as 
to practically neutralize the primary flux, 
and tin- potential ai the service brushes will 
be zero. As the effeel of the primary flux is 
practically neutralized, the current in the 
short circuited brush circuit will fall to zero. 

This type of generator may be wound 
either for series self excitation or for separate 
shunt excitation. 



For series self excitation the field cores are 
purposely made very small in cross section 
in order that saturation may be reached 
quickly, after which the primary flux increases 
less rapidly than the tertiary. In Fig. 4 the 
shape of the characteristic of the series wound 
generator illustrates this feature. 

At no load the potential is that due to the 
residual magnetism only. As the load comes 
on. the potential rises until saturation is 
reached, after which, the tertiary flux in- 
creasing more rapidly than the primary, the 
curve begins to droop; but as the current is 
still rising in the service brush circuit, and 
consequently the excitation, there will still 
be some increase of primary flux. It is for this 
reason that the volt-ampere curve is less steep 
than if the primary flux were derived from a 
ci instant excitation. 

The poles are laminated and purposely made 
massive and are cut away at a point corres- 
ponding to the location of the service brushes 
to provide a weak field for good commutation. 

The highest no load voltage obtainable is 
by the use of cast iron for the magnet frame. 
This, in an ordinary generator, would result 
in an increase in weight, but in the Rosenberg 
generator the cross section of the iron need 
be no heavier than consistent with actual 
mechanical strength, as the pole cores are 
small. 

For a shunt separate excitation the cross 
section of the field cores is designed for the 
proper density of the primary flux, and the 
field is excited from a constant potential 
source, for projector use it appears that this 
is the better practice and a comparison of the 
curves shown in Fig. 4 will illustrate the point 
in question. 

As already explained, in the series self 
excited generator, while the primary flux is 
limited to a certain extent by a reduction of 
ross section of the field core, then- is 
still a rising held and the droop in tile char- 
acteristic is no1 as steep as i1 would be if the 
primary (lux were derived from a constant 
excitation. The current in the short circuit 
brushes, however, dors n,,t reach so greal .* 
magnitude. 

In tile shunt separately excited generator, 
the droop in the characteristic is more steep 
and tlie origin of the curve much higher. 
The disadvantage oi this form of excitation is 
the high current in the short circuit brushes at 
no load. This high short circuit current at no 
load causes abnormal sparking at the short 
circuit brushes, and would be a serious matter 



ROSENBERG GENERATORS 



11 



were it not possible to easily limit n at no 
load by the use of a simple automatic switch 
which reduces the excitation and consequently 
the primary tlux. The main switch could 



are in contact, when the current flowing will 
keep the crater hot ready for starting at a 
moment's notice without actually developing 
a crater, as there will lie no arc. 



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Fie. 2 



also be so designed as to short circuit the 
generator when opening the load circuit, 
which would entirely take care of the sparking 
were it not for the period between closing the 
switch and the actual start- 
ing of the lamp, or the short 
time necessary for the car- 
bons to teed together. A 
reference to the motor cur- 
rent curve m Fig. 3 will 
also show that economy is 
a second reason for short 
circuiting the generator 
removing t he load, as 
;enerator requires the 
minimum amount ol energy 
to drive it when actually 
short circuit e< 1 

This feature, the ability 
to short circuit the generator 
with safety, and withoul 
-en-, us increase in current. 
makes the Rosenberg type 
of generator of special value- 
in Coast Artillery service. 

It is possible to occult 
the light by feeding the 
carbons together until they 



Furthermore, it removes the necessity for 
any protective devices in the lamp circuit, 
as the current can increase but a small 
amount above the normal, and the load 















































































































































































































































































































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Amocr-e* 

Fie. 3 



42 



GENERAL ELECTRIC REVIEW 



on the generating plant is decreased rather 
than increased by a short circuit on the 
Rosenberg generator. 

It is also on account of the small increase 



current conditions with the speed varied 
between the same limits. 

An analysis of all the curves shown indi- 
cates that for projector use the Rosenberg 

























































































































































































































































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Fig. 4 



in current at short circuit above the normal 
that the shunt separately excited generator 
is preferable. 

In order to compare tin- 
degree of regulation obtain- 
able with the Rosenberg gen- 
erator with that obtained by 
rheostatic regulation, a sec- 
tion of the Rosenberg curve 
taken from Fig. 3 is plotted 
in Fig. 2 in dotted lines. 

The curves shown in Fig. 
5 illustrate the performance 
of this type of generator with 
a varying speed. 

The left-hand curve was 
taken from a 1 kw. generator 
series self excited, and the 
1 varied between 800 and 
2400 r.p.m. It will be noted 
that the output current in- 
creases considerably, but not 
marly as much as would be the 
case in an ordinary general i ir 

The right-hand curve was 
taken from the came machine, 
shunt separately excited, and 
here we find nearly constant 



generator wound for separate shunt exci- 
tation provides the highest degree of regu- 
lation combined with stability. 




JOO _ 

Fig. 5 



41? 



TRANSMISSION LINE CALCULATIONS 

Part IV 

By Milton XV. Franklin 



LINE CAPACITY 

In any given system of electrical conductors 
a potential difference between two of them 
corresponds to the presence of a quantity 
of electricity on each, the one bring positive 
and the other negative. With the same 
charges, the P.I), may be varied by varying 
ical ; en en1 and magnitudes 

also by introducing various dielectrics. 

The constant connecting the charge and 
the resulting potential is called the Capacity 
of the System and this may be calculated in 
the cases of a few sample geometric forms. 

Capacity of an Isolated Thin Cylinder 
Lei /._./., (Fig. 10) be a thin cylinder. 
Let Q be the electrostatii > harge per cm. of L,L,. 
l.< • Qdy be the charge on element dy at p. 

Let tp be Ian 2- 

r 

Then the distance P p<=r sec <f>, 
and if dF, be the force exerted by Qdy on unit 
charge at P 

(r sec)- r 2 r w 

The component of dF,Jperpendicular to L,L, will 



be dF, cos <j> = ^ cos 3 <j> dy = dF 
and 



f 

I 

JL, 



4>dy 



(-') 



(3) 



but 










<t> = 


r 






\ I 




whence: 






F 




c 






I ( \ 




= Qr 


r 


V 




L A 


J/, 



(4) 



(5) 
the 



In the case of a transmission line i 
Li ii .1 h may 1" finite, and the 

values of L 2 and L, in (4) may be represented 
by l oc and x ively, thus: 



(6) 




The potential at a point in the vicinity of a 
charged cylinder is defined as the work 
necessary to bring a unit charge to tins poinl 
from a point at which the force due to the 
charged thin cylinder vanishes. From (6) 
it will be seen that F=0 when / -= v. , i.e., 
the force vanishes at co . 

The potential at point I' may now be 
defined as the work done in bringing a unit 
charge from infinity to /'. 

Work = force x distance, whence, 

dW r =Fdr (7) 

from (6), 



Wr = 



X r 



= 2Q \ln rl°°=2Q {In oc - In r) 

= C-2<Jhir (S) 

C is an infinitely great constanl and (8) 
shows that the potential at P cannot be 
determined from the conditions given alone. 
The potential at the surface of the thin 
cylinder, whose radius may be taken as p, 
will be given by: 

Wp=C-2Q In p ,'.<i 

From (8) and (9) the difference in potential 

may be calculated thus: 

W 



V 



-\\',= 2Q(lnr-hi p) 2Q/»1=V (1(1) 

is the potential 
t-2 



—P 



\ 



N 



y 

i 



Lt 



\ 



difletvnce between the 

surface of tin- 
conductor of 
radius p and l he 
poinl /' distanl 
r i ' ' cen- 

ter oJ i he con- 
d uctor. t h e 
potential at P 
being >hu- solely 

rad~' ii. If there 
exist 01 I 

ges in the vicinity the potential a1 P will be 



\ 



»^ 



io. 



\ 



V 



--H. 



FiK. 10 



r 



UnX+ O 



(ID 



ents the char;.. 
X represents the distances of /' from the \ 

char. 

C is an infinitely large constant. 



u 



GENERAL ELECTRIC REVIEW 



The potential difference between two paral- 
lel cylinders (Fig. 1 1 1 equally and oppositely 
charged may be calculated as follows : 

Let V, be the potential at P due to B, 

Let l', be the potential at P due to !'• . 
From (9) 

\\ = C-2QlnX 

V.,= -C+2Qln(d-X) 
From (11) 

V = 2Qln(± X \ 



(12) 



when /' is at the surface of B 

I 



„„(V) 

similarly at B., 

(t^»)- 



V t =2Qln(- ''' 



r 

d--r 



(13) 



(1-1) 



the potential difference between the surfaces of 
B, and B 2 is (13) -(14) thus 
d-r 



V = 



In 



■ In 



.1 



) 



2 Q ( I 

Capacity is defined as the ratio 
from (15) 



Q 



(15) 



whence 



C- 



iQ »(r?) H d r) 



(16) 



where C is the capacity per unit length 

d is the distance between conductor centers 
r is the radius of each conductor 

and Q is the charge per cm. length of two 
parallel conductors, in a medium whose spe- 
cific inductive capacity is unity. In actual 
calculations an imaginary line is devised and 
the capacity of the wire with respect to this 
line is called the capacity of the wire. 

The capacity of either wire with respect to 
an imaginary line situated in the vicinity may 
be found from (12 |(13): e.g. the capacity of 
#, with respect to the line bisecting the plane 
of centers of B X B 2 is calculated as follows: 

From (13) V, = 2 Qln ( ' ' "\ 

Prom (12) Vp = 2Qln(4^*\* 2Q In 1 0(17) 



From (15) V =.2 Qln 

B, and P 

From (16) C = 



( ¥■) 



2 In ( 



P.P. between 



(IS) 



V) 

Equation (17) shows that the above 
imaginary line is of zero potential: for this 
reason the line is called the neutral line and 



also for this reason it is situated parallel to 
and midway between the line wires and is the 
imaginary line selected, in the case of a single- 
phase, two-wire line. 




Fig. 11 

Equation (18) shows that the capacity of a 
single wire and the central line is two times 
that of the two wires considered as a con- 
denser. 

The significance of this is evident from the 
relation 

( ! 



V 



(19) 



which shows that the potential difference 
varies inversely as the capacity, and therefore 
the potential difference between B, and the 
neutral line, being one half that between 
B l and B 2 , the capacity between B x and the 
neutral line will be two times that between 
B, and B.. 

The values given in (16) and (18) are for 
absolute units, i.e., capacity in farads, per 
centimeter for an interaxial distance given 
in centimeters and natural logarithms. Re- 
ducing to units of 10(1(1 feet and to common 
logarithms the expressions (16) and (IS) 
reduce respectively to 

3 677X (lO) - ' 



C = 



(20) 



C 



<-(''/) 

farads per 1000 feet of 2 parallel wires, and 
7 354 • (10)-' 

(V) 

farads per 10(1(1 feel of one wire and neutral 
line. 

A three phase three-wire transmission line 
spaced at the corners of an equilateral tri- 
angle behaves as regards capacity precisely as 
though the neutral line were situated at 
the center of the triangle. This has been 
proven experimentally by Perrine & Baum. 

For three parallel wires equally spaced, 

in a plane the neutral or zero potential 

line moves harmonically between the positions 

midway between the other lines and the 

er line. 

Tables t 1 _' ■ (26) give the capacities for 
solid and stranded conductors respectively. 

(To be Continued) 



45 



EXHAUST FAN BLOWERS FOR RESIDENCE FURNACES 

By R. E. Barker 
Small Motor Department, General Electric Company 



The ordinary hot-air furnace is used very 
widely for heating residences and usually 
performs an economical and satisfactory 
service. There are. however, cases where the 
natural air currents from the furnace do not 
rly heat all parts of the house. In 
nearly every installation some rooms may be 
found which cannot be comfortably warmed, 
although excessive quantities of fuel are 
burned. The length of irv<\ pipes, direction 
and force of the wind outside, etc., all have 
their effect in impairing the heating afforded 
by the furnace. The exhaust fan blower is 
offered by the General Electric Company 
as an easy means of relieving such conditions. 
It often proves to be a very effective 
remedy. 

The device is well shown in the illustration 
and consists of a moderate speed motor 
driving a six blade fan in a supporting frame. 
The apparatus is supplied with an attaching 
cord and plug, and thus connections to the 
ordinary lighting circuit may be made with 
ease. No special wiring is required, as the 
motor takes no more power than one sixteen 
candle-power incandescent lamp. 

The above mechanism will undoubtedly 
improve the heating effect of the average 




Fan Blower for Residence Furnace 

hot-air furnace, and as its cost of operation is 
very low it will show a considerable saving in 
fuel consumed. Instead oi piling on extra 
coal when the weather becomes severe, the 



extra heat required may he moved through 
the piping system by the action of the furnace 
blower without any appreciable increase in the 
fuel burned. The heat which under usual 
conditions remains in the cellar is taken up by 
the air forced through the pipes by the fan and 
is sent to the rooms above before the heat is 
lost. 

These motors are furnished for the following 
circuits: 



ALTERNATING CURRENT 

Size Cycles 

12 in. tid 

11' in. m 

12 in. 41) 

12 in. in 



SINGLE-PHASE 

Volts 

110 
221 I 

120 
220 



DIRECT CURRENT SERIES WOUND 

12 in. 1100 110 

12 in. 1100 220 

The outfit should be installed in the cold 
air box or duct near its junction with the 
furnace. To receive the motor, an opening 
I4f in. by 8f in. should be cut in the top of the 
box. This hole should be fitted with a 
hinged door or lid. with the hinges set back to 
allow the iron cover of the outfit to rest on 
the box when placed in the operating position. 
In mild weather, when the motor is not 
required, it may be easily removed and the 
opening closed by the hinged cover. The 
handle on the top of the motor support 
provides a ready means of moving the appar 
atus when necessary. 

Among the several good features possessed 
by this blower, the following may be mentioned : 

.Simplicity of construction. 

Ease of installation. 

Ouietness of operation. 

Low cost of operation. 

Saving of fuel. 

Xo special wiring required. 

Moderate first co^t. 
This outfit in its complete and special form 
is the result of a practical tesl ol the appli- 
cation herein described. This statement 
may be somewhat reassuring to a prosp' i 
buyer to whom the theory appeals but 
who is doubtful of the results to be obtained 
in actual practice. There is nothing experi- 
mental either in the outfit itself or in the 
manner of its use. 



46 



GENERAL ELECTRIC REVIEW 



TRANSMISSION LINE CONSTANTS 

Part VII 



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VOL. XIII, NO. 2 



Copyright, 1909 
■ ■, ml u . - u i 'ompany 



FKBRl'ARY. 1910 



CONTENTS 



Editorial 

Atmospheric Electricity 



By Prof. Elihu Thomson 



The Relation of the Steam Turbine to Modern Central Station Practice . 

By G. R. Parker 

The E Rotary Condensers on Power-Factor 

By John Liston 

Transmission Line Calculations, Part V 

By Mil ion W. Franklin 

Commercial Electrical Testing, Part IV 

By E. F. Collins 

A Financial Statement of the Cauvery Hydro-Electrical Development, India 

A Motor I Iperated Rail Mill 

Bv B. E. Slum i 

Some Points of Modern Practice in Induction Motor Construction 

By E. L. Farrab 

ng Machine Motors- Drawn Shell Type 

By R. E. Barki b 

Oil and Transformer Drying Outfits 

By E, F. < i i 1 1 km us 



51 

53 

62 
67 



Ol.it 



uarv 



76 

84 

s.s 

"1 

92 
95 
96 




STEAM ENGINEERING DEVELOPMENT 

The history of the development of the 

steam engine is similar to that of all man's 
inventions and, unlike natural evolution, has 
proceeded from the complex to the less 
complex. Nearly 150 years ago James Wan. 
the Scotch engineer, may be said to have 
inaugurated the art of steam engineering 
by his invention of the condenser. The rapid 
advance that has been made during the last 
century in reciprocating engine practice, and 
during this century in the development of 
the steam turbine, are indeed largely owing 
to his genius, while the modem high power 
triple and quadruple reciprocating engines 
are the natural offspring of the cruder and 
more complicated arrangements employed in 
steam engines in Watt's time. 

During the last decade steam engineering 
has made a further notable advance. The 
steam turbine has been successfully developed, 
and has already superseded its one-time 
rival, the reciprocating engine, in manv 
branches of the art . Possessing no reciproca- 
ting parts and with a far simpler and more 
compact construction, it would undoubtedly 
have come to the front sooner had mechanical 
and electrical engineering been sufficiently 
advanced to cope with the constructional 
difficulties incident to the high speeds re- 
quisite and to npen a field for its sendees. 
With the advent of high speed generators, 
the latter difficulty was removed and 
mechanical engineering has been forced to 
solve the new engineering problems involved 
in the manufacture of the turbine. 

The reciprocating engine, owing to its 
construction, is neither theoretically nor 
practically the best or most logical form of 
prime mover. Due to cylinder condensation, 
it wastes steam, while it is unable to utilize the 

ater pan .1 the large amount of energy 

available in the steam at low pressures in 

consequence of the small limits which are 

practicable for expansion. It occupies con- 

rable space per kilowatt on put owing 



to separate cylinders being employed for 
each expansion and to the fact that high speeds 
are not possible with heavy reciprocating parts, 
and piston speeds are limited by various prac- 
tical considerations. The piston engine is, 
indeed, a far more complicated machine than 
t ie steam turbine and is not so well adapted 
to modern power requirements. It is unable to 
utilize the steam energy below about 26 in. 
of vacuum and rejects practically all energy 
below this pressure. When it is realized 
that the steam energy available between 28 
in. and 29 in. vacuum is as much as 19 per 
cent, of the total steam energy at 200 lbs. 
gauge pressure, it is evident how much the 
reciprocating engine is handicapped in this 
respect. 

As pointed out in Air. G. R. Parker's 
excellent article in this issue on steam turbine 
development, the steam turbine does not 
labor under this disadvantage, and it is due 
to the better utilization of the steam energy 
at low pressures that the turbine has made 
such rapid strides in commercial engineering. 
It is already installed in the greater number 
of large steam power plants in this country, 
and at the present time the total capacity 
of high pressure Curtis turbines of 500 lew. 
and over, manufactured and sold by the 
General Electric Company, exceeds 1,400,000 
kw., representing a total of 740 units or an 
average capacity of about 1900 kw. for each 
machine. 

The smaller amount of coal, fewer station 
attendants and boilers necessitated, and the 
smaller buildings required by turbine stations 
of a given capacity, are now realized; but it 
is instructive to calculate the saving that 
can be effected by a turbine station by apply- 
ing actual costs of a Curtis turbine tation and 
a representative modern engine station, to a 
vet tation of average capacity. Suppo 
ion of 20,000 kw. is cr, n id, red operating 
Lbout -to per cenl load fa< toi : 

The following results .arc based on figun 
tined under actual operating conditions, 



52 



GENERAL ELECTRIC REVIEW 



which in nowise favored the turbine station. 
The quality of coal was approximately the 
same in both cases and the water facilities, 
station capacity, load factor, etc., nearly 
equal. The costs were also averaged over 
about 4 months' operation so as to obtain 
representative operating conditions. In the 
turbine station, the labor bill per kw. hour 
was only slightly greater than 25 per cent, 
of that of the reciprocating engine station, 
while the coal bill was only about 80 per cent., 
with the total cost of operation standing at 
less than 65 per cent. Applying these figures 
to a 20,000 kw. station, the following sums 
will be saved per annum bv the turbine 
station; viz., S40,000 for coal, 860,000 for 
labor, with a gross saving, including main- 
tenance charges, of $110,000 per annum. 

Besides dealing with high pressure turbines, 
Mr Parker describes the exhaust turbine and 
the latest development of this type; namely, 
the mixed pressure turbine. The enormous 
increase of capacity, without increase in 
coal bill, and in some cases with an actual 
decrease in the latter item, which can be 
obtained by using low or mixed pressure 
turbines in connection with either condensing 
or non-condensing reciprocating engines is 
clearly exemplified. The reasons for the 
economical operation of this turbine with 
high pressure steam are also given. The 
article finishes with a review of the field 
filled by the small turbine in capacities of 
300 kw. and less, the conclusion being that 
such turbines have negligible maintenance 
charges owing to their very durable con- 
struction. 

In reference to the exhaust and mixed 
pressure turbines, it is of interest to note 
that over 50,000 kw. have been sold to date, 
the average machine capacity being slightly 
greater than 1400 kw. So undoubted are 
the economies that can be derived by in- 
stalling such turbines, that it is certain thai 
no reciprocating engine stations with con- 
densing facilities can long afford to do with- 
out them, especially as the mixed pressure 
turbine is exceedingly flexible in operation 
and will on emergency continue to deliver 
power, though tlie supply of low pressure 
hi from the reciprocating engine is 
entirely cut off. 



A MOTOR OPERATED RAIL MILL 

The Gary Works of the Illinois Steel 
Company form the nucleus of what promises 
to be the largest steel manufacturing center 
in the world. The works are ideally located 
both for the reception of the raw material 
and the disposal of the product, as their 
situation on the shore of Lake Michigan 
permits the delivery of the ore directly 
from the lake boats to the works' storage 
pile; while in addition to the readiness by 
which the product may be shipped by water, 
the proximity to the city of Chicago, with its 
numerous intersecting railway lines, places 
the exceptional transportation facilities of 
that great distribution point at their com- 
mand. 

At the present time the following mills are 
completed or in process of construction: 

A continuous rail mill 

A continuous billet mill 

A 60 inch universal plate mill 

An axle mill 

Four merchant mills of 10, 12, 14 and 18 
inches respectively. 

Each of these installations embodies many 
new features, both in the design of the mill 
and the methods of rolling the steel. 

The article by Mr. Semple in this issue 
is the first of a series that will describe these 
various installations, and covers the rail 
mill, which was the first to be put in opera- 
tion and is one of the most important as well 
as interesting of the several mills to be 
installed, as it marks a new era both in the 
steel and electrical industry, being the first 
in which rails are rolled entirely by electric 
motors directly from the ingot without re- 
heating. The motors, furthermore, are not 
only larger but several times larger than 
any other motors previously built. 

Few undertakings having the magnitude 
of these works and involving as many 
radically new features have experienced so 
little trouble in operation as this mammoth 
steel plant. In this connection, by no means 
the least conspicious among the departures 
in engineering are the large rail mill motors, 
the operation of which has been successful 
from the first day they were put in com- 
mission. 



;,;: 



ATMOSPHERIC ELECTRICITY 

By Prof. Elihu Thomson 



From the remotest times the thunder- 
storm has been one of the most impressive 
of natural phenomena, inspiring terror in 
men and other creatures alike. The real- 
ization of its interest and grandeur is prob- 
ably of comparatively modern origin. It 
is indeed not surprising that in pagan 
mythology the lightning stroke was as- 
cribed to the anger of the greatest of the 
gods. It is no wonder that, in one of the 
grea nis of the Bible. Job is asked. 

"Canst thou send lightnings that they may 
go and say unto thee. ' Here we arc'"'" 

With the decay of authority and miracu- 
lous interpretation of natural phenomena 
and the gradual growth of rationalism and 
scientific study the recognition of the light- 
ning and the thunder as a result of natural 
processes gradually came about. In the 
seventeenth century began that gradual 
awakening to the possibilities of the con- 
quest of nature, the outcome of which is 
modern science with all its great achieve- 
ments. It was the period of Bacon, Gali- 
leo, Gilbert, Descartes, Newton and others. 
At first the explosive action of lightning, 
the noise of the thunder and the subsequent 
strong smell of ozone, which often exists, 
suggested a kinship with gunpowder, or 
that certain nitrous and sulphurous con- 
stituents of the atmosphere supposedly had 
become fired. This naturalistic view even 
the s< It constituted witchcraft exponent, 
Cotton Mather, willingly adopts in one of 
his books. 

Priestly, the discoverer of oxygen gas, 
in his "History of Electricity," published 
in 1 7i>7. makes an interesting quotation 
from a paper of a certain Dr. Wall in the 
Philosophical Transactions. This Dr. Wall, 
an experimenter in electricity in the latter 
half of the seventeenth century, and a con- 
temporary of Otto Guericke and later of 
Newton, after describing his experiments 
with rubbed amber and the production of 
light and the cracklings therefrom, says, 
"Now. I make no question but upon using 
a longer and larger piece of amber, both 
the cracklings and light would be much 
greater." Then further he says: "This 
light and crackling seems in ■ ome degree 



•Address al the formal opening of the Palmer PI 
Laboratory at Princeton University, Oct. 21, 1909. 



to represent thunder and lightening." I 
believe this to be the first reference to the 
possible relationship between elect rich v 
and lightning. The later history of Frank- 
lin's suggestion of identity, D'Alibard's 
experiment and that of the famous kite 
furnishing experimental proof, are too well 
known to be dwelt upon hen' 

The practical genius of Franklin led him 
at once to the suggestion of protection from 
lightning by means of a conducting rod of 
metal, well connected to the moist ground 
at its lower end, and projecting beyond the 
!. ghest parts of the building or structure 
to be protected. In these later years it is 
not unusual to meet with statements of dis- 
credit or denial of the efficacy of this simple 
device. There seems to be a tendency 
among the uninformed to regard it as an 
old-fashioned and useless if not a dangerous 
contrivance. Often the question has been 
asked whether it is not an exploded notion 
that such rods have any value for protec- 
tion. It may well be that the "lightning- 
rod agent" of former times is largely re- 
sponsible for the distrust. He was a sort 
of confidence man, who supplied a sham 
appliance, often of marvelous makeup. A 
structure of twisted metal tube topped with 
glittering gilt points in clusters, mounted 
on green glass insulators, the whole as ex- 
pensive as the unhappy victim could be 
frightened into paying for, was erected, 
and often left without any adequate con 
nection to the ground. It was a tree with- 
out roots; lacking, in fact, the most essen- 
tial part of its structure. 

Le1 us add with emphasis that the Frank- 
lin rod when properly installed undoubt- 
edly secures practical immunity from light- 
ning damage. Its installation is an engi- 
neering undertaking demanding study of 
varied conditions and proper care and 
judgment in meeting these conditions. The 
one consideration originally left ou1 was 
that if there were any better or more dired 
paths for lightning existing in the building 
or structure, or better ground connei 
than the rod possessed, these must be in- 
cluded in the protective system. Bui it is 
also a fact that the construction of most 
modern buildings, particularly in cities, " 
volves so much metal in roofing, ventilating 
and Other pipes, wires and the like, that it 



54 



GENERAL ELECTRIC REVIEW 



is generally unnecessary to resort to any 
separate means for protection. 

In cities there are many lofty structures 
framed in steel, piping that projects above 
the roof, and metal stacks, generally in 
good connection with the underground pipe 
systems; all of which together tend to mini- 
mize danger from strokes of lightning. 
The best vindication of Franklin will, how- 
ever, be found in the fact that the firmest 
reliance is placed by the trained electrical 
engineer upon the provision of an easy 
path for the electricity of lightning to 
reach the ground. Practically all his pro- 
tective appliances or arresters used in elec- 
tric systems are based on that principle, 
with modifications and additions to suit 
particular conditions of use. To provide 
such modifications and adaptations is 
by no means an easy task. There is still 
a possibility of insufficiency such that 
the menace of breakdowns and damage 
by lightning still remains a bete noir to the 
engineer. The tremendous discharge of 
energy possible in a lightning stroke may 
be sufficient to defeat our efforts. Break- 
ing through insulation and causing short 
circuits, burning of wires and rupture of 
circuit, and damage to apparatus are still 
occasional experiences in spite of our safe- 
guards. Even at a considerable distance 
away a stroke of lightning, by its inductive 
action, may set up electric waves or surg- 
ings which require to be provided against. 
The extremely uncertain value of the ef- 
fects, the irregularity and impossibility of 
calculation or prediction, render the prob- 
lem of protection difficult. The effects of 
these secondary surges are generally incom- 
parably less violent than direct strokes, and 
they are seldom dangerous to life. 

So long indeed as our electric lines are 
extended above the ground, so long must 
this disturbing factor be reckoned with. 
Fortunately it has been possible by con- 
stant effort and study to secure more and 
more effective appliances so that the light- 
ning menace grows steadily less. Research 
and experimentation in this direction have 
constituted an important part of the devel- 
opment of electrical engineeri 

Having thus at some risk of your pa- 
tience vindicated our earliest worker in the 
study of atmospheric electricity — Franklin 
— let us turn from the practical issues and 
consider the electricity of the air from a 
more general standpoint. 



The study of the nature and origin of 
electrical storms or disturbances through- 
out the atmosphere is of much interest; 
our knowledge is yet meager; there is much 
more yet to be learned in this fascinating 
field. Exploration of the electrification of 
the air at varying heights by captive bal- 
loons, by kites, and upon elevations of land, 
has generally shown an increasing electric 
potential upward from the earth, and usu- 
ally positive in relation thereto. Sometimes 
this relation is reversed. It has been 
roughly estimated that if the differences 
noted can be assumed to be extended to 
include the total depth of the atmospheric 
layer, the earth's surface might be negative 
to the surrounding space, 150,000 volts 
more or less. This condition would not 
admit of being regarded as constant or 
stable, since widespread electric storms 
occur in both our upper and lower air 
levels. In the highest regions of our at- 
mosphere they take the form of diffuse dis- 
charges as in a high vacuum and are called 
auroras. They either accompany or give 
rise to magnetic storms, which affect the 
direction and intensity of the earth's mag- 
netism temporarily, and hence disturb the 
compass needle, sometimes through many 
degrees. Within a few weeks past we have 
experienced such a storm of a remarkable 
intensity; sufficient in fact to cause inter- 
ruptions to telegraphic and cable transmis- 
sion during several hours. Brilliant au- 
roras were at the time seen in some 
places. 

The frequency of auroral phenomena, 
and perhaps also to some extent the fre- 
quency of thunder-storms, seems to keep 
pace with the sunspot period, at least in 
our latitudes. At times of sunspot activ- 
ity, the surface layers of the sun, u] 
the energy radiated from which so much 
of earthly activity depends, are stirred by 
great storms, or immense cyclones of hot 
gas or metallic vapors; storms seem as 
dusky spots on the sun's disc. They can 
attain enormous size— 20,000, 30,000 or 
even 50,000 miles in diameter, though these 
dimensions are exceptional. They are vis- 
ible, as is well known, not because they are 
non-luminous, but because they are less 
luminous than the surrounding solar sur- 
face. In like manner bright spots or fac- 
ulag may also be seen, because they are on 
the whole brighter than the sun's surface 
adjoining them. 



ATMOSPHERIC ELECTRICITY 



55 



There is much reason to believe that, in 
accordance with suggestions made many 
years ago, these solar storms are accom- 
panied by exceptionally vigorous projec- 
tion-outward from the sun to immense dis- 
tances, of .streams of electrified matter. 
Should the earth happen to be in a position 
to be swept by such a stream, an aurora 
may be produced. During a total solar 
eclipse the so-called coronal streamers are 
seen to extend from the sun's surface to 
distances of upwards of two millions of 
miles or possibly farther than that, bu1 
doubtless they keep on outwardly, ami in- 
visibly, to relatively enormous distances. 
It is not unreasonable as a hypothesis to 
imagine that they may extend at times as 
far as the orbil of the earth and may, if 
the direction is the proper one, reach our 
outer air. 

Further, if they consist of electric ions 
or particles conveying electric charges, an 
aurora may result. Dr. Hale of Mt. Wil- 
son Observatory, has indeed recently shown 
by the spectroscope that great solar storms 
are in fact attended by the motion of elec- 
tric ions at enormous velocities. The phe 
nomena of auroras present peculiar difficul- 

3 in their study, since, as in the case of 
the rainbow, no two obervcrs at a distance 
from each other see the same or identical 
appearances. Hence attempts to determine 
the height by triangulation at which au- 
roras exist give most contradictory results, 
for it is impossible to fix upon any con- 
densation or streamer which may not be 
displaced or absent to another observer 
some distance away. This is understood 
when we bear ir. mind that the luminous 
appearances are not located in one plane, 
but are distributed in space; condensations 
of light being the result of superposition in 
the line of observation. 

I have come to the opinion thai the 
auroral streamers often extend in a gen- 
eral direction outwardly from the earth. 
sometimes to very great distances rela- 
ly to the known extent of our atmos- 
phere. The effects observed appear unac- 

intable upon any other supposition, 
while they are consistent with the idea of 
outwardly d streams of greal < 

tent. In April, 1883, then- occurred an 
aurora which was at its maximum a little 
after midnight. It was the mosJ magnificent 
display of the kind, which, in spite of a 
continual vigilance on my pan. i1 has been 



my fortune to witness. It was upon 
such a scale that, so to speak, the mechan- 
ism of the streamers stood revealed. At 
that time I could not avoid the conclusion 
that the auroral streamers must have ex- 
tended outwardly 'several thousand miles. 
There is no space here to present the argu- 
ment involved. Perhaps the most signifi 
cant fact is that precisely the same gen- 
eral appearances were noted in Chicago as 
in the cast, and that they occurred simul- 
taneously. The interesting question arises, 
does the earth temporarily acquire stream- 
ers similar in nature to the solar coronal 
streamers? The answer is as yet unknown. 
At the time of the great display mention- 
ed there was a sunspot near the center 
of the sun's disc of abouf 50,000 miles in 
diameter. During that disturbance long 
telegraphic lines could not be operated, 
owing to arcing at the keys which pre- 
vented interruption of the circuits. Ap 
parently in subtle sympathy with its 
ter orb, the sun, the earth's electric 
and magnetic equilibrium was for a time 
profi .undly disturbed. 

While it is by no means certain that 
auroras and magnetic storms are always 
dependent on solar outbursts, it is now 
generally recognized that the observed co- 
incidences are too frequent to be the result 
of chance. It is perhaps safe to assume 
thai although solar storms and sunspots 
can occur without provoking auroras or 
magnetic storms lure, it may be doubted 
if these latter occur on any great scale un- 
less solar activity is coincident therewith, 
And it seemingly is true that only 
the projected electrified matter actually 
reaches the earth or comes ne-ir enough to 
inductively affect its electrical equilibrium 
are the terrestrial phenomena produced 
1 hereby. 

It has even been suspected that a greater 
frequency and severity of thunder-s1 
in our lower air accompanies the active 
period of the sun or sunspot maximum. 
Tins is a hypothesis which would require 
a careful collection and comparison of 
data over a long period to give it status as 

Li utitic fact or wholly to dii 
Be that as it may, experience with lightning 

Lge in electric installations seem 
supporl the idea and, in a paper given 

- i seven or eighl j eai i a lurin] 

minimum period, led me to predid a severe 
ordeal a few years in advance. As a mat- 



56 



GENERAL ELECTRIC REVIEW 



ter of fact the prediction was to a large 
extent verified with the result of extraor- 
dinary activity in devising safeguards from 
which the electrical engineering art now 
benefits. In general the harm done by 
thunderstorms is due directly or in- 
directly to the heavy spark discharges 
called lightning flashes or strokes of light- 
ning. 

It may be of interest to refer briefly to 
the conditions existing in a cloud which is 
the source of such destructive energy. As 
is well known, clouds consist of fine water 
particles suspended in the air. When frozen 
these particles are crystalline like minute 
snow crystals. All clouds above the 
snow line are likely to be of that character. 
At a temperature above freezing the 
particles of water are miscroscopic spheroids 
which may by gradual coalescence form 
drops of rain. This process of coales- 
cence necessarily diminishes the total 
surface of the water existing as such in 
the cloud. Should, however, the original 
particles possess even a slight electric charge, 
the union of the drops, by lessening 
the total surface, or diminishing the 
electric capacity, results in a great rise of 
potential or electric pressure on the sur- 
face of the drops. The process of coales- 
cence continues and the water falls out of 
the cloud as rain. If the cloud particles 
are frozen the diminution of surface and 
consequent increase of electric pressure 
can not take place. This would seem 
sufficient to account for the general ab- 
sence of thunder-storms in winter, though 
perhaps oilier causes contribute. 

A thunder-cloud has been compared to 
an insulated charged conductor, such as a 
body of metal hung upon a silk cord, but 
in reality the two are not at all com- 
parable. It is a mistake to assume any 
close analogy to exist. The cloud being 
only an air body containing suspended 
water particles, is not a conductor, nor can 
it, as in the case of metal, permit the ac- 
cumulation of its electric charge on its 
outer surface. In fact it possesses no true 
definite outer surface but blends with the 
clear air around it. The electric charge it 
possesses remains disseminated, so to 
speak, throughout, and must reside chiefly 
upon the surface of its constituent water 
drops. Accumulation in any part would 
require the insulating air between t he- drops 
to be overcome. 



A lightning stroke from such a mass 
may indeed represent a discharge of hun- 
dreds of amperes at millions of volts. We 
must, however, be cautious not to exag- 
gerate either the current or the potential 
present in a lightning flash. The current 
in a flash can at times be only a few am- 
peres or may in the heavier discharge 
reach perhaps hundreds, or possibly in 
extreme cases some few thousands of am- 
peres. It is doubtful if the potential much 
exceeds at any time more than a few mil- 
lions of volts as it is probable that small 
local breakdowns start the disruptive pro- 
cess which then extends through miles of 
length. The individual water particles even 
when collected into drops can not be 
charged to such enormous potentials as 
millions of volts. In reality it is the com- 
bined effect of the numerous particles act- 
ing inductively that accounts for such 
pressures. A combined stress is set up 
towards the earth or towards another cloud 
mass of opposite charge. The lightning 
stroke results from a breakdown of the in- 
sulating air layer between them, and also 
all through the cloud itself, and for a time 
a partial neutralization or electric equi- 
librium is effected. This continues until a 
further redistribution of charges is re- 
quired and until again the breakdown 
potential is reached. The continued coa- 
lescence of charged water particles which 
were not discharged at the first breakdown 
repeats the original condition, and so on. 
Unlike the case of a suspended charged 
metal body, a single discharge does not 
usually equalize the electric potential of 
cloud and earth. Instead, many succes- 
sive discharges occur. It is probably 
fortunate for us that the process is as 
gradual as it is, for the ordinary partial 
discharges of the cloml are each terrific 
enough and tax our resources sufficiently 
when we seek to protect ourselves and our 
effects from them. 

Various hypotheses have been proposed 
to account for the presence of electric charges 
in cloud masses, but there is no time to 
discuss them here, and there is in fact 
little that is really known as to the 
origin of the electricity of clouds. We 
shall briefly refer to the phenomena which 
characterize or accompany the electric 
discharges. The usual form which the 
discharge takes is t hat known as disrup- 
tive spark or fork lightning, a long flash or 



ATMOSPHERIC ELECTRICITY 



57 



ric spark, joining earth and cloud, or 
cloud and cloud, and branching within 
the cloud mass like a tree. Oftentimes 
between cloud and earth there is seen the 
streak zigzag in its course, but 
within the cloud it ramifies or branches 
extensively in several directions, In this 
way only can any considerable pan of the 
cloud contribute its portion to the 
discharge path, for, as stated before, the 
cloud act as a conducting body. 

irities treat lightning as a dis- 
charge of very high frequency like the 
ordinary discharge of a condenser or 
Leyden jar. In fact, it has no1 been un- 
usual i" assume thai such apparatus can 
be substituted and inferences drawn as to 
the nature and character of the lightning 
discharge from experimentation and tests 
with these laboratory appliances. There 
is, however, abundant reason to doubt that 

ning discharges are really oscillatory. 
If they oscillate the conditions are such as 
to forbid such oscillation being of a high 
frequency order. The cloud discharge 

sents what is known as a discharge 
of a large capacity, and the length of the 
path or spark may reach thousands of feet 
or even many miles, a long inductive 
path; while the heat and light given out in 
every part of the path indicate a high resist- 
ance to the passage of the discharge. 
All of these conditions are together 
known to be inconsistent with the idea 
of high frequency oscillation. But the 
breakdown or discharge is extremely sud- 
den and involves an almost instant rise 
of the current to a large value, so that 
the inductive effects upon surrounding 
. such as electric lines or cir- 
cuits, are very energetic and sharp like 
a quick blow struck; and these lines or 
structures become the seal of rapid vibra- 
or high frequency oscillations. The 
sudden blow of the hammer on a bell in 
Eke manner brings out all the rates of the 
vibration, fundamental and overtones, of 
which the bell is capable and in which the 
hammer itself takes no part. 

The very sudden startling character of 
a lightning discharge leads to an i 
geration in the popular estimate of its 
more evident i fl The amount of light 

given out is not so great as is often as- 
sumed, h does not give 
parable with full sunshine. While doubt- 
less the intrinsic brilliancy is very high the 



duration of the flash is small, generally 
only a minute fraction of a second. In 
photographs of lightning the landscapi is 
generally seen only in outline or poorly 
lighted by the discharge. In the daytime, 
when the clouds are not dense enough to 
greatly darken the sky, the Hash lose-. 
of the blinding character it has when seen 
in the blackness of night. Similarly, the 
sound of thunder, though of terrifying 
quality, is not extraordinarily loud. It is 
a common experience when traveling in a 
train to note thai the sound of even near-by 
flashes is smothered by the roar of the 
train so that no thunder is heard. The 
of thunder can not be due in any 
part, as is sometimes erroneously assumed. 
to collapse of the air upon itself and into 
a partial vacuum left by the spark. I have 
seen this error even recently repeated and 
even extended to include all the noise of 
thunder as due to such collapse. When, 
ver, we consider that in a minute frac- 
tion of a second the air in the path of the 
discharge is so highly heated that, if it 
were confined, its pressure due to heal ex- 
pansion alone would rise to more than ten 
atmospheres we can readily understand the 
explosive shock given to the surrounding 
air and the propagation therethrough of an 
intense air wave. In fact such waves from 
electric spark discharges and from dyna- 
mite explosions have been clearly recorded 
by photography. Moreover, that the col- 
lapse of the air after expansion can have 
little or no effect in the sound production, 
follows from the fact that the heated gas 
Streak left in the path of the discharge 
takes an appreciable time to cool on ac- 
count of its low radiating power. This is 
shown by the observation that a lightning 
discharge in dusty air is often succeeded 
by a luminosity of the streak which per- 
sists for a perceptible lime and slowly fades 
away like the luminous trail of a meteor. 
Another common misconception is that 
he prolonged rolling character of thunder 
is due to reverberations or echoes. In 
mountain regions with steep rock walls 
such reverberations possibly contribute to 
thi effect, but it is now clearly recognized 
that a sufficient single explanation su 
for mos1 eases. Owing to the great I 
ot the lightning spark oi path, we receive 

i the dis- 
charge far m advance ot that from the 
more remote portion., and between 



58 



GENERAL ELECTRIC REVIEW 



sounds are'those from parts of the path at 
intermediate distances from the observer. 
It follows from this that no two observers 
at a distance from each other hear the 
same succession of sounds in the thunder 
of a discharge. Whenever portions of the 
discharge path are situated or extended in 
an approximate direction at right angles 
to the line from the observer, the sound 
from that part of the path is louder or of 
high amplitude owing to the sound from 
that part of the path reaching the observ- 
er's ear at the same instant. Whenever the 
path leads directly away from the observer 
the amplitude is less, the sound is less ex- 
plosive and takes the character of an ex- 
tended roll or rumble. 

It will be seen from this that every twist 
and turn and every change of direction of 
the spark path with respect to the observ- 
er's position gives a varying loudness and 
sequence of sound. Every branch of the 
main discharge in like manner records its 
position and direction, its twistings and 
bendings in these sound vibrations and 
sequences. It would seem possible even to 
record on a phonograph noises from sparks 
invisible to the eye and map the positions 
of tin- sparks in space from records so pro- 
duced. If this were done as it were 
stereoscopically or stereographically from 
two or more separated observing or record- 
ing places, the records would contain the 
necessary data for the reconstruction of the 
spark ami i t s branches in space. 

From the above considerations an at- 
templ to determine the distance of a light- 
ning stroke to earth by counting seconds 
.lapsing between the Hash and the first 
thunder and allowing five seconds to a 
mile approximately is seen to be futile. 
Should one of the cloud ramifications or 
branches of the great tree-like discharge ex 
tend in the cloud overhead with relation to 
the observer, and that part of the dis- 
charge be nearer to him than any other he 
will first hear a receding rumble above 
him, followed it may be by a heavy ex- 
plosion from the mam or approximately 
vertical spark between cloud and earth and 
from the pans of which his distance is 
nearly the same. This louder explosion 
will then be followed generally by a pro- 
longed rumble of diminishing loudness which 
is the sound coming from the ramifications 
which lead farther to the distant parts of 
the cloud. .Manifestly the counting of lime 



should be between the flash and the heavy 
explosive sound due to the vertical part 
of the flash. 

Bearing in mind that over the extent of 
cloud the charged water particles may be 
said to be waiting for a chance to dis- 
charge to earth, it is not surprising that 
any path which has been opened or broken 
down by disruption of the insulating layer 
of air should serve for the discharge of an 
extended body of cloud. The heated vapor 
or gas in the path of the discharge is a 
relatively good conductor of electricity, 
serving to connect the cloud mass to the 
earth below. The significance of this is 
understood when it is known that many 
lightning discharges are multiple. In- 
stead of a single discharge they consist of 
a number rapidly following one another 
through the path or spark streak opened to 
them by the first discharge. This first dis- 
charge opens the way or overcomes the 
insulating barrier to the discharge of por- 
tions of the cloud mass, which, on account 
of remoteness or lower potential, could not 
themselves have caused the breakdown. 
These repeated or multiple flashes are ex- 
ceedingly dangerous, both to life and prop- 
erty. The first discharge may reduce wood 
to splinters and the subsequent ones set it 
on fire. The time interval between the 
successive discharges in such a multiple 
flash is quite variable and may be Ion- 
enough to he easily perceptible by the eye. 
The multiple character is easily disclosed 
by the image in a revolving mirror. If a 
strong wind be blowing at the time of such 
a multiple flash, the hot gas conducting 
the discharges may be displaced later- 
ally in the direction of the wind with the 
result of spreading out the discharges into 
a ribbon more or less broad. Photographs 
of these ribbon flashes show their true char- 
acter plainly; each separate dischai 
pearing as a streak of light parallel to the 
others and at varying distances apart. In 
fact parallel discharges of exactly the same 
contour are sometimes observed many fi 
apart. Here the hot gas of the first dis- 
charge has evidently been shifted by 
wind over a considerable space before the 
second and subsequent discharges took 
place. Heavy ram seems to weaken the 
air ami help to precipitate a discharge. 
Prom the fact that strokes of lightning are 
en followed by increased fall of iain 
within a few seconds it is a prevalent idea 



ATMOSPHERIC ELECTRICITY 



59 



that the increased downpour is caused by 
tin- discharge. In reality the reverse is the 
case, for jusl when a gush of rain has 
reached from the cloud down to within a 
hundred feel or mure from the ground, by 
far the major part of the air layer has been 
so weakened electrically by the presence of 
the water drops, that the discharge itself 
anticipates the completion of the distance 
of fall of the rain, and is therefore a short 
time in advance of the time when the de- 
scending gush of rain actually reaches the 
ground. As. the gusts or gushes of rain 
are more or less local and sweep along with 
the storm cloud, they are apt to mark out 
the places of the most frequent lightning 
strokes. Shelter sought at such times 
under tall trees is particularly dangerous. 

The amount of energy which may be 
concerned in a lightning discharge is 
neither definite nor capable of estimation. 
It would seem that the widest variations in 
energy may occur and this would account 
largely for the observed differences in the 
severity of the effects. It must be remem- 
bered also that by far the larger part is 
expended in the long spark in the air and 
cloud. Even when much damage is done 
to objects struck it is only a small fraction 
of the total energy which is expended on 
them. Most of the damage to property 
ies indirectly from the electric discharge 
by its energy being instantaneously con- 
verted mil heat. This heat evolves steam 
and expanded gases in the- interior of such 
materials as wood and causes explosion, 
shown in the splintering or rupture. 

A curious effect, often noted when a tree 
is struck and shattered, is that when the 
splinters, sometimes of large size, are 
thrown bodily out to distances of many 
feet from the shattered tree, the splinters 
in their movement remain parallel to the 
tree and in a vertical position. They are 
,111-111 lv found standi Lgh1 after a 

stroke and at distances ranging up to sixty 
or eighty feet away. This fact indicates 
that the projecting force is quite instan- 
taneous and is exerted equally and at the 
omenl throughout thi length of the 
splinter in a direction transverse to its 
length. Sir h splinters are sometimes ten 
or twelve feet in length and several inches 
thick. As will he seen, a person near a 
large tree which is so disrupted ..s m danger 
ol being struck in a different wa_ , even if 
he escapes being included in the path oi the 



stroke itself. Aside from this mechanical 
danger it is known that to take refuge 
under a tall tree during a heavy thunder- 
storm is particularly hazardous. This is 
so because the human body is a better con- 
ductor than the tree trunk, particularly as 
tin- trunk itself is the last part to become 
thoroughly wetted by the rain. The leaves 
and upper parts are wet and more or less 
conducting while the tree trunk itself may 
be yet dry. In such a case the body of a 
person forms a good path or shunt to the 
dry trunk and is therefore particularly apt 
to be traversed by any stroke which reaches 
the tree. 

As before indicated, damage to buildings 
and other such structures can in all cases 
be prevented by the provision of an effect- 
ive shunting path to earth. A most essen- 
tial feature of such a structure as the Frank- 
lin conductor is its good connection with 
the ground, or better its connection with 
what we know as a good ground. In 
early times it was considered that it was 
quite important that the tip or upper end 
of the conducting rod should be sharply 
1 min nd, or should bristle with sharp points, 
so to speak. The tips were gilded and the 
points made of gold or platinum to prevent 
rusting. The points were supposed to draw 
off the lightning silently from the cloud 
and so prevent strokes of lightning. But 
for millions of volts at cloud distances 
almost all irregular objects on the surface 
of the earth are practically pointed. Per- 
haps on this erroneous assumption of the 
action of points as applied here little stress 
was laid on the direct path to earth being 
chosen and on the necessity of including 
with it or connecting to it other good paths 
such as gas pipes, bell wires and the like. 
There is no need of any special provision 
of points. A blum end will do as well, for 
after all there is practically no silent dra 
ing off of the charge from the cloud, for it 
is no1 an insulated conductor. The pro- 
vision of a lightning conductor on a building 
undoubtedly increases its chances of being 
struck by lightning, but if properly ar- 
ranged it also ensures that the structure 
shall suiter no harm therefrom. Viewed 
from our present standpoint it is a curious 
historical fact that in 1777, just after the 
war of the American revolution broke out. 
a miniature verbal war between the advo- 
cates oi blunts a Ints, respectively, as 
applied to lightning conductoi raged In 



60 



GENERAL ELECTRIC REVIEW 



England party politics led many to con 
demn points as revolutionary and stick to 
blunts. The Royal Society by majority 
vote decided for points, but those who so 
voted were considered friends of the rebels 
in America. George III. took the side of 

ats. Franklin, who from the first had 
prescribed points, wrote from France: "The 
King's changing his pointed conductors 
for blunt ones is a matter of small import- 
ance to me. For it is only since he 
thought himself safe from the thunders of 
Heaven that he dared to use his own thun- 
der in destroying his own subjects." The 
king is reputed to have tried to get Sir 
John Pringle, then president of the Royal 
Society to work for blunts, but received the 
reply: "Sire, I can not reverse the laws 
and operations of nature." As stated 
above, it matters not at all which we may 
use. I have, indeed, seen a number of 
cases in which the sharp points of lightning 
conductors had been melted into rounded 
ends by lightning. 

In the foregoing we have been consider- 
ing the effects of such ordinary discharges 
of electricity as the disruptive spark, or 
zigzag flash. Apparently if the testimony 
is reliable there are ether and more rare 
forms of discharge. I allude to sheet light- 
ning, so-called globular lightning and to 
bead lightning. But it may be asked, why 
call sheet lightning a rare form? It is, 
indeed, true thai when a storm is so far 
distant that the spark discharges can not 
be seen, as when ii is below the horizon, or 
when the spark is blanketed by a mass of 
mist of cloud there is to be noted a diffused 
light or extended illumination, which, on 
account of distance, may not appear to be 
attended by thunder. This and similar 
effects are often called sheet lightning. 
From observations during a few heavy 
storms, however. I am led to infer the exist- 
ence at rare intervals of a noiseless dis- 
charge between cloud and earth — a silent 
effect attended by a diffused light, and 
which may be the true sheet lightning. In 
my experience it has accompanied an un- 
usually heavy downpour of rain, the whole 
atmosphere where the rain fell most heavily 
being apparently momentarily lighted up 
by a purple glow, seemingly close at hand 
in the space between the rain drops. The 
appearance has been seen in the daytime 
as an intense bluish or purplish momentary 
glow without any accompanying sound. It 



could scarcely have been illusory. It is 
hoped that other observers will carefully 
note any such like effect if it occurs. It is 
certainly a rare phenomenon. 

It is quite common that any very bright 
flash, the details of which from its sudden- 
ness and intensity are unobservable, be 
alluded to as a ball of fire. Doubtless 
many of the reported cases of so-called ball 
or globular lightning may be explained as 
instances of this condition of things. 
Nevertheless, there are so many recorded 
instances, apparently in substantial agree- 
ment, that it is difficult to escape the con- 
clusion that there in reality exists this rare 
form of electric effect, globular lightning. 

We can not properly discredit observa- 
tions of phenomena which are so rare that 
our own chance for confirmation of them 
may never come. We must, in such cases, 
carefully scrutinize the testimony, exam- 
ine the credibility of witnesses and their 
chances of being mistaken. It is certainly 
impossible at present to frame any ade- 
quate hypothesis to account for this curious 
and obscure electric appearance. The wit- 
nesses agree that it is an accompaniment of 
thunder-storms and that it resembles a ball 
of fire floating in the air or moving along a 
surface, such as the ground. It is not tie- 
scribed as very bright or dazzling, and the 
size of the ball itself may be from an inch 
or two to a foot or more in diameter. 
Observers agree that it can persist for some 
time and that its slow movement allows it 
to be readily kept under observation while 
it lasts. When it disappears there is usu- 
ally an explosion and a single explosive 
report like that of gun fire. Sometimes it 
is said to disappear silently. Usually the 
damage done by its explosion is only slight. 
This summary of characteristics is common 
to all accounts. Some accounts are even 
more detailed, mentioning that the fiery 
ball seemed to be agitated or with its sur- 
face in active motion. I have found two 
instances occurring many years apart and 
in widely different localities in which it is 
described as having a reddisli nucleus, in 
diameter some considerable fraction of the 
whole. The outer fiery mass has been de- 
scribed as yellowish in color. In some 
instances it has been seen to fall out of a 
cloud. It is described as entering build- 
ings and moving about therein. Person- 
ally I was for a long period in doubt as to 
the reality of this strange appearance, 



ATMOSPHERIC ELECTRICITY 



61 



deeming it the result of sonic illusion, or a 
fanciful myth. But on hearing descrip- 
tions by eye witnesses known to me as per- 
sons not given to romancing, and finding 
their accounts to correspond closely with 
the best detailed descriptions in publica- 
tions, my doubts have disappeared. 

In one instance, while observing the 
lightning during a heavy thunderstorm, a 
companion, whose eyes were turned in a 
direction nearly opposite to my own, sud- 
denly called to me that a ball had just 
dropped out of the cloud some distance 
away. The view of the ground was ob- 
structed by buildings and I unfortunately 
just missed it. The noise of its explosion 
was, however, heard in the direction indi- 
cated by my fellow observer, as a single re- 
port like the tiring of a gun. At the time 
I closely questioned him as to details of the 
appearance. Our ignorance of its possible 
nature is complete. No rational hypothe- 
sis exists to explain it. Science has in 
the past unraveled many obscure phe- 
nomena. The difficulty here is that it is too 
accidental and rare for consistent study, 
and we have not as yet any laboratory 
phenomena which resemble it closely. 

Sometimes photographs taken during 
thunderstorms have been found to carry 
curiously contorted streaks in some de- 
gree resembling lightning flashes. Gener- 
ally they have been found on plates upon 
which undoubted lightning discharges have 
been recorded. In some instances which 
have come to my notice the streaks have 
had the appearance of a string of dots or 
beads and have been taken to represent a 
very rare form of lightning known as bead 
lightning. A number of such photographs 
have been submitted to me for opinion as 
to the nature of the curious streaks. In all 
cases they are explained as due to the camera 
having been moved without capping the 
it ting images of lights, such 
as arc lights, or spots of refle< ted light 
from wet or polished surfaces to traverse 
the plate in an irregular course. They 
are then only records of the inadver- 
tence of the lightning photographer. In 
one instance the effect was so curious that 
it was several years before the true ex- 
planation was found. In that case th 
were two wavy contorted streaks of per- 
fectly parallel and of similar outline, but 
unequal in intensity, rising ead from a 
rail of a single track railway, and appar- 



ently terminating in the air fifteen or twenty 
feet above the tracks. They were finally 
traced to a moving camera, and a re- 
flection from the wet and polished rail 
surfaces of the light of an arc lamp lo- 
cated outside the field of view. It required 
a visit to the place itself to enable this con- 
clusion to be reached. The particular 
beaded streaks or lines of dots were traced 
to the fact that the arc lamps causing them 
were operated by alternating currents 
which naturally give light interrupted at 
the zero of current ; one hundred and 
twenty times per second being the usual 
rate. All this emphasizes the need of care 
and wholesome scrutiny or even skepticism 
before reaching a conclusion in such cases. 
is bead lightning, which has at times 
been described as observed visually, a real- 
ity 5 If it is. it appears to be even rarer 
than the globular variety. Perhaps it is a 
string of globules ; a variety of globular 
lightning. But we can not make assump- 
tions. As in the case of globular lightning, 
there is some testimony, which can not be 
wholly disregarded, tending to show that a 
form of discharge resembling a string of 
beads can actually exist. An account of 
an instance was given me within one hour 
after the occurrence itself. The witness 
was known to me as perfectly reliable. The 
appearance was described as a festoon 
of finely colored oval beads hung as it were 
from one part of cloud to another, and as 
persisting for some seconds while gradually 
fading away. The opposite ends of each 
bead were said to be different in color. It 
was seen during an afternoon thunder- 
storm and spoken of as very beautiful, and 
altogether different from the usual zigzag 
flash. 

If I have dwelt upon these exceptional 
appearances at sonic length it is because 
they seem to show that in electricity there 
is much y 1 to learn and abundant oppor- 
tunity for future investigation. It i 
tainly literally true that, in the langua 
of Shakespeare, "There arc more things 
in Heaven and earth, Horatio than arc 
dreamt of in your philosophy." Such work 
belongs to the science of physics, now- ri 
nized as fundamental in all study ol 
ture's processes. In . '■ ering, 

which is in reality an ail based upon ap- 
plied physics, the subjed ol lightning pro 
m has alwaj s been one ol i < : len ble 
if not vital importance. Just as a light- 



62 



CEXERAL ELECTRIC REVIEW 



ning discharge from a cloud clears up a 
path for other discharges to follow, so in 
electric undertakings it opens up paths for 
the escape of the electricity we are sending 
out to do the work intended, such as for 
lightning, power or other use. In the 
past, disablement of machinery in electric 
stations has not been rare. The recent 
growth of long-distance transmission in- 
volving hundreds of miles of wire carried 
on poles J across country, over hills and 



through valleys, has set new problems of 
protection, and called for renewed activity 
in providing means for rendering the lines 
and apparatus immune to the baneful ef- 
fects of electric storms. Judging the 
future by the past, we may conclude that, 
whatever difficulties of the kind arise, in 
the great future extensions of such engi- 
neering work, science and invention will 
provide resources ample for the needs, and the 
rapid advance will be continued unchecked. 



THE RELATION OF THE STEAM TURBINE TO MODERN 
CENTRAL STATION PRACTICE* 

By C. R. Parker 



Since the commercial introduction of the 
steam turbine into this country some seven 
years ago, so much has been said and written 
on the subject that it seems almost super- 
fluous to attempt to add anything to the 
already large store of general information. 

To a large number of readers a review 
of steam turbine principles will, therefore, 
be merely a repetition of ground covered 
many times. But in any branch of science 
an occasional brief return to basic principles 
is never out of place. 

The objective of designers of all classes 
of steam prime movers has been the same; 
namely, the conversion of the heat of com- 
bustion into mechanical or electrical energy; 
and the medium employed has been water. 
It is true that the overall efficiency of our 
best steam prime movers is rcgretably low, 
due to the fad that so much heat has to be 
given to water before any of it can be con- 
veiled into mechanical work. For example, 
the total heat per pound of steam at 150 
lb. gauge pressure is about 1195 B.t.u. 
If steam be expanded to a 28 in. vacuum 
the total energy available in this range is 
only aboui 321 B.t.u. This 32] B.t.u, is 
all of the total heat we are able to use, and 
in prai in i commercial machines may convert 
anywhere from one-half to three-fourths of 
this available energy into mechanical work. 

In this country we are interested chiefly iii the 
Parsons and Curtis types of steam turbines. 
Briefly, the Parsons principle involves thei 
tinuous expansion i,t steam through alternate 
rows of moving and stationary blades, the 
former being attached to the spindle and 

* A Paper read 1 m crican 

Society of Mechanical Engineers and the St. Louie Engineers 
Club, December 11, 1909. 



revolving it . and the latter redirecting the st earn 
against other revolving blades. The expan- 
sion of the steam thus occurs in both moving 
and stationary blades and motion is given 
the rotating element, both by the impact 
of steam on the moving blades and its 
reaction on leaving them. The machine is 
ordinarily called a reaction turbine and 
may in a general way be compared with a 
reaction water wheel. 

The Curtis principle differs from the 
Parsons in that the expansion, instead of 
being continuous throughout the machine, 
is broken up into a series of pressure steps 
or stages. Each one of these contains a row 
of stationary nozzles which expand the steam 
through a certain range and direct it with 
large velocity against the moving buckets, 
through which it passes with practically 
no further expansion, thus moving the 
revolving buckets by impulse only. The 
expansion of steam, therefore, occurs only 
in the stationary element. This type of 
turbine is referred to as the impulse type 
ami is somewhat analagous to the impulse 
water wheel. It is with the impulse turbine 
as invented by Curtis ami perfected by 
Emmel thai this present paper deals. 

The problem confronting all turbine de- 
signers has been to reduce tile speed to such 
an extent that the turbine itself and the 
generator connected with it could be 
made to safely withstand the centrifugal 
strains. Other speed limits are imposed by 

tlie commercial electric frequencies in use 
in this country. Evidently 1500 r.p.m, is 
the highest speed for a 1'.") cycle generator 
and 3600 r.p.m. for (id cycles. 

The most efficient speed for any single 
impulse wheel driven by a moving liquid or 



RELATION OF STEAM TURBINE TO MODERN' CENTRAL STATION PRACTICE (>:"i 



gas is one hah thai of the moving element. 
Steam exhausting from a pressure of L50 
lb. gauge through a suitable nozzle attains 
a velocity of aboul mini feel per second. 
Therefore, half this speed, or 2000 feel per 

>nd, should be the corred peripheral 
speed of a single impulse wheel placed in the 
the steam jet. Evidently such a 
peripheral velocity would necessitate an 
angular velocity far in excess of the highesl 
commercial speeds. To reduce this high 

■ilar velocity ami at the same time retain 

efficiency of his machine, Curtis made use 
of two expedients. The first consisted 
in utilizing the velocity of a single expansion 
in nmre than one wheel, and thus dividing 

initial velocity into two or more parts. 
This reduced the peripheral speed of each 
wheel in inverse proportion t«> the number of 
wheels. However, there are practical limits 
to the number of wheels which can be util- 
ized in a single expansion; therefore, to still 
further reduce the speed, Curtis not only 
divided the velocity of a single expansion 
into two or mere steps, but divided the 
total expansion range into two or more 
separate expansions. • 

A considerable amount of experimenting 
was done in the early days of manufacture 
to determine the correct number of stages 
an<l wheels per stage. Thus the first large 
turbines built contained two stages and three 
rows of revolving buckets per stagj. Later 
investigations shi >wed tha for all large turbines 
m«isi economical results were obtained 
with n<>t mure than two rows of buckets per 
stage, and this is the present standard. With 
the exception of very large machines, four 
stages has been -egarded as the correct 
number, although recent experiments in- 
dicate that possibly greater economy may 
be obtained with one or more additional 
stages. 

of the principal and most justly 
founded claims for the steam turbine is its 
relatively high economy a1 other loads than 
rated load. Even in the best designed 
reci] >roi a ngines thi besl e© >n< 'my is 

obtained at one point and at loads greater 

less than this, cm off occurs either too 
early or too late for thi cylinder proportions, 
and the result is a steam consumption per 
horsepower relatively higher ai these loads. 
Since very few power loads can lie made to 
hold constant at any given poim the average 
economy on a varying load may be consider 
ably in exci ss of the besl obtainable value. 



On the other hand, the Curtis principle 
permits Inch economy at all loads. This is 
due largely to the method of governing. 
M i I impulse wheels have partial peripheral 
admission of steam; i.e., Steam flowing 
through only a portion of the wheel at one 
time. Thus in the Curtis type the nozzles 
expanding the steam and admitting it to 
the first stage wheel extend over only a small 
portion of the wheel periphery. These 
nozzles are generally placed close together 
in a single continuous arc, although in the 
very large sizes two groups of nozzles spaced 
L80 apart are employed. The admission 
ot steam to these nozzles is controlled by a 
corresponding series of valves which vary 
in number according to the size of the 
machine. The opening or closing of these 
valves evidently permits the passage of 
steam through a greater or less number of 
nozzles. The steam emerging from two or 
more nozzles combines to form a continuous 
belt or stream of steam of constant width, 
determined by the width of the nozzles, and 
of length corresponding to the number of 
nozzles open. Governing is thus accomplished 
by automatically varying the length of this 
steam belt by the successive opening or 
closing of the admission nozzles. The steam 
thus arrives at the point of inlet at lull 
pressure, regardless of the load, and whether 
one or all the nozzles are open it is expanded 
with practically no throttling. The result is 
evident in the steam consumption curves. 
At fractional loads the steam consumption 
is relatively good, and as the load is increased 
the economy continues to improve, the load 
water rate curve gradually becoming a 
nearly straight line. With such a machine it 
is possible to operate over a1 least half the 
range oi the machine with maximum and 
minimum economy varying not more than 
rive per cent, from the average. The advan- 
tages of this feature on a fluctuating load 
an obvious. 

The question is open asked as to what 
are the most economical steam conditions; 
i.e., initial pressure, vacuum and superheat. 
While there is much discussion on these 
points, the present American practi© is 
becoming, reasonably standardized. As to 
vacuum, there is no question that it is worth 
while getting the hi rtainable. Tv 

eighl inchi properh pi .iking. 2 in. 
ib olute) and even higher vacuum can 
readily be obtained with modern condensing 
apparatus steam pressures vary from 150 



64 



GENERAL ELECTRIC REVIEW 



lb. to 250 lb. gauge. In the smaller and 
medium sized plants probably 150 lb. to 
175 lb. is about right, while in the larger 
ones 175 lb. to 250 lb. should be em- 
ployed. 

The arguments for and against superheat 
are numerous, but the consensus of opinion 
is inclined to favor a reasonable degree of 
superheat, at least in the large and medium 
sized plants. Superheat ranging from 50° 



and increase in speed, have greatly reduced 
the size and weight per kilowatt. About 
six years ago the first large turbines were 
installed in the new Fisk Street Station of 
the Chicago Edison Co. The first three 
machines were vertical two-stage machines 
of 5000 kw. capacity, and the fourth, in- 
stalled somewhat later, was of the same 
capacity but of the five-stage type. Within 
the last year these four machines have been 




12,000 Kw. Curtis Turbine. This machine replaced a 5000 Kw. Curtis Turbine 

of older design, the original foundation and base being retained. 

Three of the old machines are shown in the background 



F. to 200° F. is in common use. Regarding 
high pressure and high superheat it should be 
borne in mind thai the percentage increase 
of available energy given the steam is much 
greater than the percentage increase in 
fuel necessary to produce these conditions. 

Modern steam turbine practice has ad- 
vanced so rapidly in the past few years that 
quite startling changes have been etleeled 
in some of the original turbine stations. 
Improvements in details of construction, 



removed and replaced by four vertical 
machines of 12,000 kw. continuous capacity 
each. These occupy no greater space than 
the original machines, and no increase in 
the capacity of boilers supplying them was 
necessary. The Fisk Street Station now 
contains altogether ten similar machines 
of 12,000 kw. each. The Quarry Street 
Station of this same company at presenl 
contains three vertical machines of 14,000 
kw each and three more will be installed 






RELATION OF STEAM 'IT RHINE TO MODERN CENTRAL STATION PRACTICE 6." 



during the coming summer. The economies 
ted in these plains are reflected in the 
rates which the Commonwealth Edison Com- 
pany is able in make its consumers. 

A somewhal similar evolution is now under 
way m Si. Louis. In 1!M)."> the present 
Union Electric Light and Power Company 
installed two 5000 kw.. .")()() r.p.m., 25 cycle, 
6600 vuli vertical turbines. Later, two more 
5000 kw. machines were added, but with 60 
cycle, 2300 1000 voll generators. The pres- 
ent plan, which is now well under way, is 
to replace all four machines with other 
turbines of 12,000 kw. capacity each. 

The natural question is, can it possibly 
be a good business proposition to throw out 
four large turbines which have been in use 
only three or four years? That the answer 
was affirmative was due to three principal 
considerations. 

i 1 1 The larger machines could be in- 
stalled without increase in floor space. 

i_'' The improvement in economy rep- 
resented an annual charge which, if capital- 
ized, would mor< than pay for the additional 
investment. 

Practically no new auxiliary apparatus 
or station piping would be required. 

That these considerations were based on 
t assumptions has been amply demon- 
strated. The first L2.000 kw. turbine has 
now been in commercial operation for several 
weeks. 

In making this installation not only was 
it possible to utilize the original foundations, 
hut even the base of the old turbine, which 
also constitutes the exhaust chamber and 
step bearing support, was utilized in building 
the larger machine. It was, therefore, not 
ary to remove this base from the 
ete, or break the connection to the 
condi riser. In a general way it may be said 
thai the old 5000 kw. turbine was lifted 
bodily from its exhaust base and a 12,000 
kw. machine installed in its place, without 
disturbing the condenser piping and auxili- 
aries. The increase in capacit) means that 
in this portion of the station the kilowatt 
i" r quare fool of station lias been more than 
doubled, liven the original four 5000 kw. 
machines were plain! unusually close to- 
r, and '"lull the remaining three are 
ell by larger machines, it senns prob- 
able that the turbine portion of the Union 
ric Light and Power Company --tat ion will 
show a greater kilowatl capacity per square 
fool than any other station in this country. 



Aside from the increase in capacity, the 
improvement in steam economy is very 
large. Unfortunately, detailed test figures 
are not available at this lime, but it is 
probable that the new turbine will show an 
improvement of a1 least 20 per cent, over the 

one which it replaced, besides having a 
flatter load curve. On this basis considera- 
tions "I' economy alone would have warranted 
I he change. In addition, this enormous 
increase in power has been effected without 
any considerable change in the existing 
piping and auxiliary arrangements. 

Any steam turbine operating condensing 
with the usual pressure and vacuum derives 
roughly half of its power from the expansion 
i steam from boiler pressure to atmosphere, 
and the other half from the remaining 
expansion from atmosphere to vacuum. 
Thus in a four-stage machine, atmospheric 
pressure is reached between the second and 
third stages. A reciprocating engine operat- 
ing under similar conditions would not de- 
rive its energy from the steam in this pro- 
portion. The average engine actually de- 
velops some 15 or 20 per cent, of its power 
fromtheexpansionof steam below atmosphere. 

A consideration of these facts brings us 
to the low pressure turbine. In a general way, 
it may be stated that a low pressure turbine 
is that part of the high pressure turbine which 
normally operates below the atmospheric 
line. In general, it is possible to build a 
low pressure turbine for compounding with 
a non-condensing engine, with the expecta- 
tion of approximately doubling the capacity 
and halving the steam consumption, while 
the same thing may be done with a con 
densing engine to a less extent. Must 
condensing engines can be operated at their 
full capacity non-condensing with a slight 
adjustment of the valve gear. The increase 
in steam consumption of the engine alone 
with this arrangement will be between 15 
and 25 per cent .; but the low pressure turbine 
adds 90 to LOO per cent, capacity, so thai the 
mi economy effected is worth going after 
regardless of the tremendous increase in 
capacity. Installations of this chat 
were first made in this country four or live 
years ago, although greater interest has 
stimulated during the last year or two. 
One of the early installations was in the 
plant of the Last St. Louis ami Suburban 
Railway Company, where an 800 kw. and a 
liioii kw. low pressure turbine were installed 
in i - mnection wii h ni 



66 



GENERAL ELECTRIC REVIEW 



The most notable installation is that 
recently made in the power house of the 
Interboro Rapid Transit Company in New 
York City. This station contains the highest 
type of reciprocating engines, operating under 
the best possible engine conditions and 
developing an economy comparable with the 
best engine station in the country. It has, 
however, been possible to install in connec- 
tion with one of these engines a low pressure 
turbine with a nominal rating of 5000 kw. 
It is probable that a detailed report of this 
installation will be published at an early 
date. For the present it is sufficient to say 
that the improvement in steam consumption 
of the combined engine and turbine has 
effected a saving in coal consumption of 
over 20 per cent, and the combined capacity 
has been more than doubled. The turbine 
generator is of the induction type and runs 
permanently in parallel with the engine 
generator. With this arrangement it is 
unnecessary to provide any speed governor 
on the turbine. The engine governor takes 
care of both machines. It is interesting to 
know that in spite of the size and special 
character of this installation the machine 
was started and placed in commercial service 
without a hitch of any kind. A second 

achine of similar characteristics, but with 
a larger generator, is now being installed in 
connection with the second engine, and the 
present plan contemplates one turbine for 
each engine throughout the station. When 
complete, the station capacity will have been 
more than doubled without any increase 
in real estate or building investment. 

What has been dime in this connection 
can be accomplished on a smaller scale in 
almost any plant of 300 kw. or larger, operat- 
ing reciprocating engines either condensing 
or non-condensing, provided proper con- 
densing facilities arc available 

A valuable feature in connection with 
the Curtis low pressure turbine is that, -owing 
to the fact thai even with low pressure 
steam the primary admission nozzles only 
extend a portion of the way around the wheel 
circumference, it is possible to equip any 
low pressure machim with another set of 
nozzles primarily designed to expand steam 
from boiler pressure instead of from at n 
pheric pressure. A machine so equipped can 
be operated ither as a strictly low pressure 
machine, or should the supply of exhaust 
steam fail entirely due to shut down of the 
engine or other reason, it can operati 



and carry its full capacity on boiler pressure 
steam alone; or it can be operated on a 
mixture of the two, in case the load exceeds 
the supply of exhaust steam. It should be 
remembered that these high pressure nozzles 
do not throttle the steam to a lower pressure, 
but are actually designed to economically 
expand it to the proper internal pressure 
of the turbine. Such a machine operating 
on high pressure steam only, will show an 
economy fairly comparable with an engine 
or turbine regularly designed for high pres- 
sure operation. The operation of tli 
high pressure nozzles is automatically con- 
trolled by the main governor, and in practice 
it has been found possible to instantly cut 
off the low pressure steam supply without 
a noticeable variation in the speed of the 
turbine. This evidently makes a most 
flexible machine and one that accomplishes 
two most desirable results at comparatively 
small cost, namely, increase in capacity and 
decrease in steam consumption. 

It is also perhaps worth while mentioning 
the enormous field which has been opened 
up by the strictly small turbine, that is, 
from 300 kw. down. These machines for 
the most part are designed to operate non- 
condensing, and the argument in their 
favor is that they are extremely simple 
machines requiring practically no attention 
or adjustment. The best proof of their 
extremely rugged construction is found in 
the fact that, out of 500 small turbines of 
1'.") and :i."> kw. capacity now operating in 
various parts of the country, a large per- 
centage are in use by the various railroads 
for electric train lighting, under which con- 
dition it is hardly necessary to say that they 
receive a minimum of attendance with very 
few opportunities for the making of repairs. 
The confidence which the railroad companies 
place in these sets is evident from the fact 
that many of the more modern Pullman 
cars are equipped with electric fixtures only, 
no provision being made tor gas light. 
Machines of this size and larger are also in 
general use as exciters for large alternators. 
Numerous cases are on record where such 
machines have run continuously for periods 
of three or tour months or more without 
at any time shutting down. 

In conclusion it may be said that the 
Curtis turbine has been built and placed in 
successful operation in sizes from 5 kw. to 
1 1,000 kw., and at the present time even 
larger machines are under consideration. 



67 



THE EFFECT OF ROTARY CONDENSERS ON POWER-FACTOR 

By Johx Liston 

While the relation of power-factor to 
the size and efficiency of prime movers, 
generators and conductors has long been 
understood by the engineering frater- 
nity, the practical application of the 
synchronous motor as a rotary conden- 
ser, to raise the power factor of systems 
having induction motor and trans- 
former loads, has lagged far behind 
other improvements in the generation 
and transmission of energy. 

The Cleveland Electric Illuminating 
Company was one of the first central 
stations to give a practical demon- 
stration on an extended scale of the 
value of rotary condensers in raising the 
power factor of systems carrying a 
heavy inductive load. Their installa- 
tions exemplify the use of unloaded syn- 
chronous motors simply "floated" on 
the system to supply leading current to 
the line and of partially loaded syn- 
chronous motors for the same purpose. 

Before describing the installation of 
rotary condensers on this system, and 
the very satisfactory results which have 
been thereby obtained, it might be well 
to outline briefly the theory on which 
these installations are based. 

Induction motors and other induc- 
tive apparatus take a component of 
current which lags behind the line pres- 
sure, and thereby lowers the power fac- 
tor of the system, while a non-inductive 
load, such as incandescent lamps, takes 
only current in phase with the voltage 
and operates at 100 per cent, power factor. 

As transformers require magnetizing cur- 
rent, they may seriously affect the power 




Fig. 2 
Turbi 




factor when unloaded or partially loaded, 
but when operating at full loa. their effect 
is practically negligible. 



Two 9000 Kw. General Electric Curtis Steam 
ne Generators in Generating Station, Cleveland 
Electric Illuminating Company 

[n order to maintain high power factor, in- 
duction motors should be run at their full 
rated load. Due to the complex industrial 
requirements of the average installation, 
most central stations have on their lines a 
group of induction motors operating at light 
loads, thereby lowering the power factor of 
the entire system. This feature of central 
station practice is sometimes rendered still 
mori serious by the desire of a customer to 
have ample power for future extension or to 
take care of heavy temporary loads, so thai 
motors of larger rating than thai actually 
required for normal opi re frequi fitly 

installed. 

The relatn e f fully loaded and li 

I loaded induction motors on power i 
is indicated 1,-. tin diagram Pig. 1. 



68 



GENERAL ELECTRIC REVIEW 




Fig. 3. 750 Kv-a. Rotary Condenser installed in a substation 
of the Cleveland Electric Illuminating Company 



The magnetizing current is nearly constant 
at all loads and is wattless, lagging 90 deg. 
behind the impressed e.m.f., or at right angles 
to thi ii which is utilized for power. 

In the figure, A Ii is the magnetizing com- 
ponent, which is always wattless,' and CB 
the power component. The angle ACB 
gives the phase relation between voltage and 

current- the cosine of this angle -jr. is the 

power factor. 

It is evident from the diagram that if the 
load is reduce. 1, the side CB is shortened, and, 
as AB is practically constant, the angle of 
lag ACB is increased. It therefore follows 
thai the ■ ■• this angle, or the power 

factor is reduced. The figure clearly shows 
the reason for the low power factor of in- 
duction motors on fractional loads and also 
shows that since the magnetizing current is 
practicall; con I ml in value, the induction 
motor can never operate at unity power 
factor. With no load the side CB (real 
power) is just sufficient to supply the friction 
and windage. If this is represented by DB, 
since AB remains constant, the power 
is reduced to 10 or IS per cent, and the motor 
takes from the line aboul .-*(> per cen 
full load current. Ii therefore follows that a 
group of li iaded induction motors can 

from the system a large currenl at ex- 
ceedingly low pow( 

The synchronous motor when used 
rotary condenser has the property of altering 



the phase relation between e.m.f. and 
current, the direction and extent of the 
displacement being dependent on the 
field excitation of the condenser. It 
can be run at unity power factor and 
minimum current input, or it can be 
over-excited and thereby deliver lead- 
ing current which compensates for the 
inductive load on other parts of the sys- 
tem. The rotary condenser, therefore, 
can supply magnetizing current to the 
load on a system while the power com- 
ponent is supplied by the generators. 

In order to gain a comprehensive 
idea of the results obtained by the 
Cleveland Electric Illuminating Com- 
pany, a brief description of the gener- 
ating and transmission system is nec- 
essary. 

Situated in the city of Cleveland, 
Ohio, which has an estimated popu- 
lation of 515,000, and extends, with 




Fig. 4. 100 Kv-a., 2300/430 volt General Electric Synchronous 

Motor Generator Set in the Plant of the National Electric 

Lamp Association. Cleveland. Ohio 



EFFECT OF ROTARY CONDENSERS ON POWER FACTOR 



69 



its suburbs, along Lake Erie for aboul 
17 miles, the generating station, with 

its substations, serves a territory of 
approximately 50 square miles. The 
steam-driven generating station is 
located on Canal Street, near the 
business center of the city. The gen- 
erating units now in service consist 
of two 9000 kw. and one 5000 kw. 
Curtis turbo-generator sets of Gener- 
al Electric manufacture, delivering 
energy at 11,000 volts, three-phase. 
60 cycles. There are, in addition, 
some reciprocating engine-driven gen- 
erators, delivering energy at 2300 
volts, three-phase, 60 cycles. Trans- 
formers step-up the e.m.f. to 11,000 
volts for the substations. 

In addition to the alternating-cur- 
rent equipment there are three 1500 
kw. motor generator sets and direct 
current reciprocating engine sets and 
a storage battery. The energy for 
that part of the city immediately sur- 
rounding the generating station is 
distributed on a direct current, three- 
wire Edison system. The balance is 
practically all alternating current, and 
is distributed to the substations at 
1 1 ,000 volts, and re-distributed at 
2300 volts, three-phase, 60 cycles. 

There are six substations, five of 
them being straight transformer 
stations, and the sixth being provided 
with a motor-generator set and bat- 
tery in addition to the transformer 
equipment; the total distance between the 
two end substations is about 15 miles. All 
of the 1 1 ,000-volt circuits are under ground, 
being placed in vitrified clay or fibre con- 
duits, the latter form having been adopted 
as a standard for all new work. The dis- 
tribution circuits from the substations at 
2300 volts for motors and lamps arc under- 
ground cables for a short distance from the 
stations, where they join to pole lines. The 
secondary lighting circuits arc three-wire, 
single-phase. 115 volts to 230 volts, and motors 
up to 5 h.p. rating are operated from the 
lighting circuits. The general inductive di 
triliution is at three-phase, 23(1(1 volts, the 
e.m.f. being tepped-down to 160 volts and 
230 volts nt the cu itomer's premisi 

The motors arc nearly all thri i phase, but 
some two-phase motors are run from 
phase transformers by means I ' a T-connec- 
tion. The ratio of alternating-current to 




Fig. 5. 200 Kv-a. General Electric Rotary Condenser installed 
in factory of the National Acme Manufacturing 
Company, Cleveland, Ohio 



direct-current load is about 2.5 to 1. The 
arc lighting load is nearly all carried by Brush 
arc vnii rat ' >r : 

It will be seen from the above that the 
operating conditions confronting the CI 
land Electric Illuminating Company are 
those which arc ordinarily encountered by 
any central station located in a manufactur- 
ing city. The fact thai more than 40 per 
cent, of the connected load consisted of in- 
duction motors, which were frequently L 
far below their rated output, had a very 
noticeable effect on the power factor of the 
system, this effect being augmented b 
numerous transformers located in the sub- 
ion and mi i he cu I i 

rious was this tl factor 

of tip y item befon the ri 

r i were in tailed varied bel wei □ 65 
and 70 per cenl . du day, and at 

night, when [the motor load was practically 



7m 



GENERAL ELECTRIC REVIEW 




10(1 Kv-a. General Electric Synchronous Motor, Belt Connected 
to a D.C. Generator- — The Ohio Ceramic Engineering 
Company, Cleveland. Ohio 



discontinued and the lighting load 
united, it rose to bet v ; and 

90 per cent. 

Realizing that these conditions 
affected both the permissible can- 
put and ion of the entire sys- 
tem, it was determined to bring tin- 
power factor as close in unity as was 
able by the installa- 
tion of rotary condensers in those 
■ul 'stations feeding induction motor 
installations, and also in the factories 
of large motor users. 

Two 2300-VOlt rotary condensers 
of 750 kv-a. rating and provided 
with directly connected exciters were, 
therefore, installed in one substation, 
and a third unit of the same rating 
was provided for a second sub 
In addition to these, four 2011 kv-a. 
General Electric rotary conden 



with directly connected exciters were 
connected to the low-tension side of 
the transformers on the customer's 
premises: the largest motor users 
on the various distribution lines being 
selected for the installation of these 
units. As auxiliaries to the rotary 
condensers, a number of synchronous 
motors partially loaded were installed, 
the kilowatt load delivered to the 
shaft varying from 50 to 75 per cent, 
of the kv-a. rating of the motor. 
These motors are used to drive alter- 
nating current or direct current 
generators for special purposes, and 
are the property of the customer, 
while the 200 kv-a. rotary condensers 
referred to above and installed on the 
i ustomer's premises belong to the 
illuminating companv. 

The General Electric 200 kv-a. 
condenser has been adopted as 
standard for future installations in 
customers' plants, but will not be 
provided except where the power 
taken is in excess of 400 h.p. 
While this is not theoretically the 
best method, it was considered advis- 
able to have a single standard con- 
denser placed in service where 
conditions warranted its use, instead 
of working out in detail a large 
number of various condenser ratings. 



h 


] 1 
















L 






yZ\ 






Jt 


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C// / /L. 


1 




Qv 






u^^k 




/ 


\ 






kr ■>' \ 




f 






l 










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t 


p r ■•■ ■'.', 


\ 1 










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t 






K/f CtJ rrer >; ■ 




' - 


' 






' L>^ "',****< 


lv?\ i / 


' 








Aj r ■ 1 • ', ■ ■ 


rSy-i2: 








3_ , _/ 


\t7.\ ... ,: . . . ; . 






< 




■\ /' 


ph^zz 


1 


' - 


' 


ZJSJf 


7 ■ 1 1 


1 i Nm 




1 






7t T±t 


x^5\ 












X-S 


J 




y 


y f\ \ 




! * 




t 




^x± 








i 




• 


1 


i i 


i 








ztz ±±:r 


±±± 








±± 


_,_±±±± 


±zl: ± 


i 




; 


±± 



Fig. 7. Power. 



1 Ml and C 
Current in 



urrent Curves for 100' ', Power-Fact' 
phase with E.M.F 



EFFECT OF ROTARY CONDENSERS ON POWER FACTOR 



71 



The condensers thus installed 
arc carefully inspected at fre- 
quenl intervals by repre- 

sentives of the illuminating 
company, but are normally 

operated by the rust tuners, 
who arc glad to pn>\ ide the 
necessary room in their 
plants, as they benefit from 
the improved regulation. 

A typical installation of 
this nature is that in the plant 
of the National Acme Manu- 
facturing Company, makers 
of milled screws and ''Acme" 
screw machines (Fig. 5). The 
motors in this plant are 440 
volt, two-phase, and have an 
aggregate rating of 1200 h.p. 
The average demand on the 
substation is approximately 
500 to 600 k\v., and prior to 
the installation of the 200 
kv-a. condenser the power 
factor was about 75 per 
cent, on this line; at the present time it is 90 
per cent. 

It will be noted that no rotary condenser 
has been located in the power house itself, 
the reason being that when a condenser is 
connected to the terminals of a generator it 
raises the power factor of the generator by 
supplying part, or all, of the wattless current 
of the load, but this wattless current has to be 
carried throughout the circuit external to 
the generator, and the condenser therefore 
will benefit only the generating equipment. 

When the condenser is installed at the end 
of a line carrying an induction-motor load 
and provided with step-up and step-down 
transformers, the condenser can supply mag- 
netizing current to the induction motors 
located near it, and, as a result, the gen- 
erators, transformers and conductors can t><- 
of reduced size, as they do not carry the 
wattless current. 

In order to obtain most economically the 
required condenser effect with synchronous 
motors installed in industrial plants these 
motors should be partially loaded so that a 
percentage of their operating cost can be 
charged to useful output. It has been found 
that a synchronous motor used in this way 
and rated at, say, 100 kw., will give the best 
results when delivering 71 kw. actual power 
and 71 wattless kv-a. 

An example of a partially loaded synchro 
nous motor is found in the plant ol the National 





































































































































































































,<. 






























L 




























* 


M 


- 






















/ 




\ 












































T7 


'/// 


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\. 
























\ 


















































/ 




































If 


- - 






















/ 










•) 






















V 






</ f en 


t 


















'i 




























t 


!fc 




















/ 


t 






\ 
















V 




1 












^S 








/ 


j 


I 




\ 


















































































. 






















■V 














~\ 












y/ 
















































~p 
























































< 


/ 
















































































































































































































































































































































































c 


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J!-, ' 









Fig. 8. Power. E.M.F. and Current Curves for 66.5' 
Current lags 30° behind E.M.F. 



Power-Factor 



Lamp Association, which is equipped with a 
100 kw., 2300 volt to 430 volt alternating 
current directlv connected motor-generator 
set. (Fig. 4.) 

At the works of the Ohio Ceramic Engineer- 
ing Company a 100 kv-a. General Electric 
synchronous motor has been installed, belted 
to a generator which loads it to about 60 
per cent, of its kv a. rating, the balance being 
utilized for condenser effect ; this motor 
operates directly from the 2300-volt, 60- 
cycle feeder. (Fig. 6.) 

Perhaps the general effect of low power fac- 
tor on the efficiency of a power system can be 
best illustrated by the current, volt and power 
curves shown in Figs. 7 and 8, which in- 
dicate clearly the relations existing between 
the impressed e.m.f. and current, at unity 
and 0.865 power factors. The product of 
volts and amperes at any instant gives the 
in .i. mi. mo Hi . \ alue of the power. In the 
curves shown, the area enclosed b the power 
curve repre ien1 energy, It will be obsi 
thai when the power factor is unity the whole 
of the power curve lie above the axis and 
ire all I he pov ei isax ailable for mechan- 
ical work. With 0.865 power factor, corre- 
ponding to a lag to 30 d i urrenl behind 

e.m.f., a small port ion of I he power tun e lie 
below the axis and the total power available 
for work is represented by the difference be 
t he are i d by 1 he power curve 

above the axis and below. This diffei 



GENERAL ELECTRIC REVIEW 



will equal the total area enclosed by the power 
curve multiplied by the power factor 0.865 
equal to cos 30 deg. When the power 
factor is zero the current lags 90° behind the 
e.m.f., and the area enclosed by the power 
curve below the abscissa is exactly equal 
■ he area above, from which it follows that 
in one complete cycle no energy is available. 
In this case the power factor is equal to cos 
90 deg. which is zero. 

If the current leads the e.m.f., similar re- 
sults will follow, as any displacement of the 
current wave in respect to its e.m.f., whether 
leading or lagging, will introduce negative 
I ii iwer loops which subt ract from the area above 
the axis and reduce the power available. 
Maximum power is obtained when the power 
loops lie entirely above the line, as in the 
rase of unity powerfactor shown in Fig. 7. 

The prompt recognition of the Cleveland 
Electric Illuminating Company of the serious 
effect of its inductive load on the power factor 
of its system and the improved general effi- 
eieney which has been obtained by the use 
of rotary condensers should appeal to every 
practical central -station manager. 

A graj hi illustration of the value of rotary 
condensers was given recently when one of 
th feeder circuits on the (.'lew-land Electric 
Illuminating Company's system was put out 
of commission during a storm, due to a tree 
calling across the line. This feeder was 
equipped with one of the 200 kv-a. condensers 
already referred to, and while repairs were 
Icing made a feeder from a different sub- 
station which was at the time carrying 
heavy load at low-power-factor, was joined 
to take on, temporarily, the additional load. 
It was found that the ammeter readings with 
this combined load were actually lower than 
they had been with a single load on the cir- 
cuit not provided with a condenser. The 
kilowatt readings showed an increase of about 
75 per cent, while the ampere readings 
dropped about 25 per cent. 

The relative cost of condensers as comp: 
with the investment losses in gem 
conduct caused by low power factor, 

of oi iur e, depends on the percenta in- 

ductive load on a system; but the conditii 
which have to be met by the average central- 
station distribution system indicate that the 
heat losses, diminished effective output in gen- 
erators and conductors, as well as the im- 
paired regulation inherent in low ac- 
tor can be nomically overcome by 
the installation of rotary condensers. 



TRANSMISSION LINE 
CALCULATIONS 

Part V 
By Miltox W. Franklin 

CAPACITY, REACTANCE, CHARGING 
CURRENT 

In equation (21) pan IV. the capacity of 
a single conductor of a transmission line was 
expressed as 



C = 



7.:m (10)" 



w(^) 



(1) 



' is the capacity per 1000 feet, in farads; 
J is the interaxial distance of the conduct' ■ ■ 
r is the radius of the conductors. 

From (19) part IV the charge in a condenser 
of capacitv C subjected to an impressed e.m.f. 
£is 
Q CE. 

Current is defined bv t= ." . whence 

at 

the- current flowing into a condenser at any 

instant, is 



. dQ = CdE 

*~ dt ~ dt 
i is the instantaneous current. 
e is the instantaneous e.m.f. 






If the e.m.f. varies harmonically; i.e., if 
E = E„ : sin {w t); (3) becomes 
. ■■ ' /'.'„, cos {m t) 



C E m si 



I uj If 



(4) 



The effective value of i is the R.M.S. and is 
expressed by 

(l /* T V 
y. 1 i J dt I . whence its value may be ob- 
tained from (4) as follows: 



W/*M r rr u ") 

'/■',„ (°-f. | cos" (io 1) d (w : j 



5 



TRANSMISSION LINE CALCULATIONS 



73 



-"•Q"Wi 1 (' )]) : 



' 1 n \ 2 -/ 

= CE m ^ -=- 

for 2 z/=cu 
But 

I- whence 

lefi = W C 






■ 



I e jj is called the charging current of the 
line and will flow into and out of the con- 
denser even when the line is on open circuit. 
The current is wattless, but nevertheless 
represents an PR loss in the system. 

In a transmission line of small length, the 
charging current is given with sufficient 
accuracy by supposing that a condenser of 
capacity equal to that of the line is affected 
by an impressed e.m.f. equal to that employed. 

Tables VIII and XXII (August and Novem- 
ber, 1909, issues of Review, respectively) give 
the values of the charging current per 1000 
volts impressed e.m.f., per 2000 feet of con- 
ductor (or 1000 feet line distance) and for a 
frequency of 100 cycles per second. Charg- 
ing currents at other frequencies and for other 
lengths of line are proportional to the respec- 
tive ratios of the lengths and frequencies in 
question to 1000 and to 100. 

In a three-phase line the capacity is equal 
to that obtained by star connected conden- 
sers each of capacity equal to that "t any 
single wire. The charging current per wire is 

thus seen to 1m- equal (approximately)to 

times the charging current lor any pair oi 
wires, of a single-phase Line. Tables XIV and 
XXVIII (September and December, 1909, 
issues of Review, respectively) give charg 
currents for three-phase lines. For any s 

rical arran I oi the n in 

tabulated will no1 dil he true 

values. 

In long transmission lim the simple 
calculation oi charging currenl 
will be found to lead to error. This is due to 
i he fad I ha1 thi i apacity oi the line is not 



entrated at a poinl and affected by the 
impressed harmonic e.m.f. but is distributed 
along the whole length oi the line, and 
infinitesimal length oi line is by a 

rd e.m.f. The e.m.f. is different a1 
i" 'int on i he line b 

at the generating end of the line is lo 
by the resistance and self-induction of the 
line up to I he poinl a1 winch it is impn 
upon the infinites mal i irmed by 

any given infinitesimal length of line, and 
may also be raised by o that 

pi iin1 . 

There is in addition to the above, a 
or actual flow of current across the space 

i i'ii the line wires so thai the currenl in 
the line at a poim distant from i rating 

end is b) .his equal to thai al 

general ing 'lid. 

The general solution oi the problem de- 
mands a consideration of the above 1 
conditions. The complete solution is 
what complicated, involving imaginary as 
well as real roots in the resulting differential 
equations (Bedell & Crehore, Alternating 
Currents, page 177' l'.\ regarding the 
vector quantities / and E as complexes, the 
pn iblem may be vi itly simple 

The general problem consists in finding the 
e.m.f. and currenl at any poinl on the line, 
having given the e.m.f. and current at an) 
other point: e.g., knowing the e.m.f. and 
current at the receiving end of the line, to 
calculate the e.m.f. and currenl a1 any poinl 
distant /. from the receiving end. 



- - -_ 



dl 



^ 




Fiir. 12 

Lei /. be die self induction in hi i unit 

lengl 

I. ei C er unit lenj 

line. 

Lei R be tl [th of 

line. 

I. el 
unit 

line 
I "l line 



74 



(VEXERAL ELECTRIC REVIEW 



is / and whose length is dl, the current and 
e.m.f. in said section are affected as follows: 



The e.m.f. drop is 

d E = IZ cos <p dl + IZ i sin • 
= 17. dl(cos <p + i sin <p) 

d E 

' = IZ(cos </>4 i sin <p) 

i(f> 



= IZ e_ 
where Z=*Jr u „ l) 



(8) 



(p = tan' 



■m 



The current flowing from line element dl 
across to the corresponding element of the 
return wire will be the current by leakage and 
the current across the small condenser formed 
by the line element <//, and is expressed by: 

dl = EZ, dl{cos c/), — i sin <p t ) 
— = EZ,(cos 0, — i sin <p,) 



where 



= EZ, . '</'. 



(9) 



Ze'<l' and Z l e~''f> 1 are complexes of the 

standard form re^** and in the presenl 
problem may be treated as ordinary alge- 
braic constants. 

* = \ 1 and is a fictitious mathematical 
operator which, prefixed to a real quantity, 
indicates that the latter is to be added 

orialb a1 an angle according as 1 lie 

sign of i is + or- . 

The typical complex quantity, 

</) • isintj)), may be best understood 
from Fig. 13: 




| /Ix/sofrea/s 



Z — \ / R-+ (oj L) 2 , is the modulus or nu- 
merical magnitude of the vector quantity 

( >P = Z(cos <f>+ i sin (j>) . 

Putting ZZ^e -'</<, = /■' 
and ZeW/Zf-itx-X*. 

From (8) 



d'E .. dl_ 

dP //l dl 

and substituting from (9) 

Similarly from (9) and (8), 
,/-7 



.//-■ 



/•■/ 



in 



(11) 



(10) and (11) are linear differential equations 
of the second order and first degree and may 
be integrated as follows: 



Taking (10) 
dP 



■-#£ 



Multiplying by 2 ■ dl 



dl 

,11 - _' /- /•: dE 



■fSXS) 

integrating 

(■:;;)' ■*»-■ 

= X*(E>-\ < , 
as the constant C is purely arbitrary. 
dE 



dl 



/\ ' /• 



dE 



= =Xdl 



V /•:■■ 4 i 

Integrating again 

log(E ' X e«l &,*) *Xl+C, 

and as C,=const. and ('., is purely arbitrary, 
the last equation may be written, 






Fig. t3 



(i #]■♦'} 



-xi+c, 



(12) 



TRANSMISSION LINE CALCULATIONS 



This expression may be simplified by use 
of i he following relations. 



sinh'x+ 1 =ci 
Put y=sinhx=* J(e* — ( 

then \J y'+i I,. - e~ x ) 
Adding (b) and (c), 



y+\ y - 1 = e* 



(b) 
(c) 



tos;ly-\ • - i \ = x = sinh 'y (from [b]) 
from this development (12) may be written 



stnfc -1 -r 

^ i 



=r = sinh •/. J+CJ 

c i 



(13) 






E = C, i/.:/; ,/ / + C) 
but sinh(Xl + C,) = 

sinh X / cosh C, l-cosh )l sinh C, 
and (14) may be written 

E = a cosh X I + 3 sink XI (15) 

Equation (11) is of precisely the same 
form as (10) and the solution will therefore 
differ from that of (10) only in the arbitrary 
constants of integration, a and 3. thus 



7 = a, cosh X l + P, sink X I 



(16) 



Of the four constants of integration, a. 

/?,, two may be expressed in terms of the 

others. 



From (15) 
dE 



dl 



/ a sinh X 1 + $ cosh A /) 






From (8) and (16) 
dE 



dl 



//,/=//, (a, cosh Xl+fl, sinh X I) 



equating (17) and (18) 

a sinh A l-t V cosh A I 

= X,a, cosh X 1+ A.,3, sink XI 

Equating coefficients 
a 

X 

and (15) becomes 

E = a cosh X l + a, X, sinh A I 



(19) 



(20) 



Similarly (16) l>ecomes 

l=a \— j- sinh a I 

A\ 

It remains to determine the values of the 
'/ and a r This may be accomplished 
as follows: 

When / = i>: i.e., at the receiving end of the 
line, the e.m.f. anil current beeome E and I 
ly, and substituting these values 
in (21 i a:; ives: 

E = a cosh o+a, X, sinh o 
whence a—E a 

Again 

I = a, cosh o+-y- sinh o 
A\ 

whence a l = I and (21) - (22 'become re- 
spectively 

E = E a cosh X l + I„ A, sinh A I 



I = I„ cosh X I + -P sinh A 1 

Al 



- 

(24) 



Tlit- quantity X I is an ordinary complex 
and the values of Eand / asjgiven in (23) - (24 
may be found by evaluating cosh X I and 
sinh X I by the aid of any table of hyperbolic 
functions of a complex variable. 

Various methods of calculating the charging 
current approximately are in use, the object 
in all of them being to lessen the labor in- 
volved in calculating exactly in any given 
case. 

Ferrine & Baum have shown that in lines 
of moderate length the error obtained in 
assuming the total line capacity, as concen- 
trated at the center, is small. 

Greater accuracy is secured by assuming 
one-half the capacity shunted across each 
end of the line. 

Still greater accuracy divid- 

ing the line capacity into six equal pan 
assuming that one part is shunted acp'ss 
each end of the line and four pans across the 
center. This is in accord with Simp 
Rule of approximation and gives an accuracy 
rarely exceeded in other calculations relating 
ie same line. 

A still greater accuracy and one rarely 
justifying the additional labor involved may 
be obtained by dividing the line capacity into 
ten equal parts and spacing them equally 
along the line. 

(7"o 6* 



70 



CEXERAL ELECTRIC REVIEW 



COMMERCIAL ELECTRICAL TESTING 

Part IV 

By E. F. Collins 
Superintendent of Testing 



Regulation Test — Speed — Voltage 

Shunt regulation should be taken on shunt 
generators. A reading should first be taken 
at no-load normal voltage; then, without 















































































































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sJ 




























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1 IT- 











Load 
Fis. 17. Speed Curves DC. Motors 

changing the i ', full load should be 

thrown on and a reading taken of amperes 
armature, volts armature, amperes field and 
volts field. Holding J full load, the voltage 
should be brought up to normal and the same 
readings taken. The load should then be 
increased to \ lull load, the rheostat remain 
ing in m as befop . and similar 

readings taken. This test is repeated for ,' 
and full load. With full load on the machine 
the voltage should be broughl tip to normal 
Without altering the position of the field 
at .the load is then taken off the machine 
and the rise in vi ved. A curve 

! be plotted with amperes armature as 
abscissae and vi 'Its as ordinates. 

li the voltage should drop to zero when ', 
load is put on the machine, the load should 
be applied in smaller increments. E 
should be kepi i1 throughout thi 

Speed regulation is important in the opera- 
tion of motors, particularly in the cas 
direct current machines. The speed on all 
is should lie adjusted while the machine 



is hot, by shifting the brushes, but should 
never be corrected at the sacrifice of commu- 
tation. It should always be adjusted for full 
load unless instructions specifically state 
i itherwise. 

If special tests are required for a motor, a 
hot speed curve should be included. Starting 
with no load arfd increasing to full load, the 
speed should be carefully read at several 
intermediate points, the voltage being held 
constant at all loads. A curve is then plotted 
with speed as ordinates and amperes as 
abscissa?. Xo load and full load points of 
the cold speed curve should also be taken. 
Pig. 17 shows the general shape of the curve. 
Sonic motors with considerable armature re- 
action give a speed curve which rises as the 
load increases. 

When speeding up motors with increasing 
1 lad, the brushes must never be shifted far 
enough to produce sufficient armature reac- 
tion to weaken the field. Careless shifting of 
brushes under load has sometimes caused 
runaways; hence care should be exercised 
when attempting this operation. 

A test of the voltage regulation of alter- 
nating current generators is sometimes made, 
but more frequently the regulation is cal- 
culated from the saturation and synchronous 
impedance curves. The method of making 
this calculation is more fully treated under 
the subject of alternating current generators. 
In making this test the machine is subjected 
to normal load at normal voltage. Holding 
the same field excitation, the load is suddenly 
thrown off and the armature voltage observed. 
The difference between this and normal vol- 
tage, divided by normal voltage, is the percent. 
voltage regulation. 

When a compound wound generator is 
ci impounded hot, a compounding curve should 
be taken after the german silver shunt is 
properly adjusted. Starting with no-load 
voltage, readings - armature, amperes 

armature, volts field and amperes field should 
be taken at ', . '., \ and full load. The load 
should then be reduced to zero by the s*me 
increments, and the same readings taken. A 
curve should be plotted with amperes line as 
abscissae and volts as ordinates. The varia- 
tion of this curve from a straight line will not 
usually exceed 5 per cent. 



COMMERCIAL ELECTRICAL TESTING 



77 



i >f the set = 



Input-Output Tests 

It is sometimes required to measure the 
efficiency of a machine or set by the input- 
output method. The measurement of the 
power input to the motor and output from 
the generator is then required. The efficiency 
Total output of generator 
Total input to motor 
The efficiency of the generator = 
Total output of generator 
(Input to motor) - (motor losses) 
The efficiency of the motor •— 

(Output of generator) + (generator losses) 
Input to moti ir 

In the case of induction motors, input-out- 
put test is sometimes taken by the string 
brake method, which will be discussed more 
fully under the heading of induction motors. 

The input-output method of measuring 
efficiency is subject to considerable inaccu- 
racy. It is not recommended and should not 
be used except under special conditions. 
It is much more preferable to ascertain the 
losses directly when reliable results are desired. 
By adding all the losses to the output at any 
load, the input for that load may be obtained, 
which, divided into the output, gives the per 
cent, efficiency. 

The resulting errors from the input- 
output method are likely to be large, since 
any inaccuracy in meters or readings in- 
fluences the results directly. In loss measure- 
ment tests, the same per cent, error in meters 



or meter readings influences thi results (.1 the 
efficii nc) - alculations indin ctly. Conse- 
quently the latter method is superior foi 
accurate determinations. 



800 



■6390 

"i 

„380 



700 §-370 



600 



500 



<0 

*400 

X 
^300 



^380 
^370 
^360 



















1 1 l l l l l I l 




















\fii// Load A.C. rata 
































































































































































- ... , 6O0KVCSO.C. 














































r I 




















! 


































































! 














1 










































— 








JVo Lood/I.C. Yo/ts 


























-J 
































- 






























1 
































1 














| 




















s 


































T 




1 


[ 






















tfolooa 600H>/ts DC. 






















\ 












f 




















5 








1 




/ 


























V 


































\ 








































V 








/ 




























V 








/ 
































V 




J 




































'. 




■ 




































/ 





















zoo 



/oo 



O / 2 3 4 3 

Amperes F/e/tf 

Fig 18. No Load and Full Load Phase Characteristic on a 

3011 Kw., 600 Volt. 750 R.P.M , 25 Cycle, 3-Phase 

Rotary Converter 



TABLE VI 
Phase Characteristic on a 300 Kw., 600 V., 750 R.P.M., 25 Cycle, 3-Phase Rotary Converter 



Volts 


Volts 


Amps. 


DC. 


A.C. 


A.C. 


COO 


378 


315 


600 


:!77 


255 


linn 


376 


210 


600 


375 


156 


600 


374 


120 


600 


373 


85 


600 


:;7:; 


65 


600 


372 


41 


600 


371 


23 


600 


370 


14 


600 


.,70 


17 


600 


369 


21 


600 


160 


35 


600 


369 


i 5 


liflll 


368 


1 16 


600 


367 


170 


600 


366 


205 



Amps. 




Field 


Field 


.75 


9] 


1.25 


150 


I 50 


ISO 


1.75 


210 


2.00 


240 


2 21 1 


265 


2.30 


_'77. 


2. in 


.".in 


.' 50 


100 


_' ."p.'i 


305 


2 60 


315 


2.65 


320 


_' 77. 


332 


3 00 





3 25 


395 


3 


120 


:: 7', 


17,11 



D.I 



600 
600 
600 
600 
600 
600 
600 



600 
600 
nun 



600 



PULL LOAD 500 AMPS. D.C 



Volts 

-i I 



384 
383 

381 
180 
179 
178 
178 
:7s 
176 
175 
174 
:7:; 
(70 






601 
570 
543 
520 

5 1 2 
51 17 
7,1 15 
7,111 
7,_'7, 
7, 17 
585 
627 
685 



Amps. 

Field 


Volts 


Field 


1 117, 


1 -'7, 


1 , 25 


1 7,1 1 


1 50 


ISO 


Jim 


7lll 


2.25 


270 


2.50 


300 


2.65 




■1 77, 




:; in, 


360 


:; 7,ii 


10 


1 on 


1,S7, 


1 7,11 


.Mil 


:, i ii i 


600 



7s 



GENERAL ELECTRIC REVIEW 



Phase Characteristic 

In taking phase characteristic curvi 
determine the field current for minimum 
input at a given load on either synchronous 
motors or rotary converters, the machine 
must be operated as a motor from some 
source of alternating current, of correct 
frequency and nearly constant voltage. A 
reading of amperes input on all phases should 
be taken with zero field on the motor, when 
this is possible. Starting with a weak field. 
volts and amperes armature and volts and 
amperes field sin mid be read, and the field 
increased by small steps until the point of 
minimum input armature current is found. 
Increasing the field current beyond this point 
increases the amperes armature. On a no- 
load phase characteristic curve, the watts 
input at the lowesl poinl should check very 

ely with the sum uf the core loss, friction 
and windage losses, since tin: power factor is 
unity on synchronous motors at this point. 
With a weak field the current is lagging and 
with a strong field it is leading. In taking a 
no-load phase characteristic the current should 
rise to a value of at least •">() per cent, of full 
load cumin. 

A I >ad phase characteristic sin iuld In- taken, 
m a manner similar in t hat employed in 

aining the no-load characteristic. The 
input is lnld constant and tin- amperes load 

orded in addition to tin- readings specified 
above. It is impossible to obtain a zero field 
point on the full load characteristic, since the 
currenl would be so large as to dangerously 
heat tin- machine and the torque n.01 sufticn ni 
irry full load. 
All readings should 1m- corrected for in- 
strument factors and shunt rat ins. and a 
curve plotted between amperes field as 
abscissae and amperes armature as <>rdinates. 
Sir Table VI and Fig. is. 

Synchronous and Static Impedance 

Synchronous impedance should be ta 
mi alternating currenl machines to determine 
the field currenl y t<> produce a given 

armature current when the machine is running 
short circuited. Since the regulation of the 
machine is calculated from the impedance 
and saturation curves, care should be taken 
that consistent results are obtained. 

The armature should first be short circuited; 
then, with the machine running at normal 
ed and a weak Iuld current, th current 
in each phase should In read. The field 
currenl should be I gradually until 

200 per eent. normal armature currenl is 



reached, readings being taken simultaneously 
of amperes armature and field, and volts field. 
Although the speed in this test should be 
held normal, a small variation therefrom will 
not affect the curve, because in the formula, 

e.m.f. E . 

current - . - = . the term 

impedance V R J + L- 1 1 '- 

l\- is small compared with DW 2 . and as E 
and W vary proportionally to the speed, the 
current remains practically constant. 

On some of the standard machines, a 
stationary impedance is taken in addition to 
the synchronous impedance. First block the 
armature or field, in the case of a revolving 
field machine, then connect the armature 
leads to an alternator giving the same fre- 
quency as that of the machine being tested. 
Starting with about 50 per cent, normal 
current, the current in the armature of the 
machine tested is increased by steps to about 
150 per eent. normal, readings of volts and 
amperes armature being recorded. 

This method should be followed in taking 
stationary impedance on induction motors, 
exi ept that it is only necessary to take one 
reading at normal current. A special station- 
ary impedance test is sometimes taken on 
induction motors: this is treated under the 
heading of induction motors. 

In the calculation of synchronous impe- 
dance all readings should be corrected for the 
constants of instruments and ratios, and a 
curve plotted on the same sheet as the 
saturation curve, amperes or ampere turns 
iuld being plotted as abscissae and amperes 
armature as ordinates. See Table VII and 
Fig. 19. 

Wave Form Potential Curve Between Brushes 

In determining the wave form of a direct 
current machine the following method should 
be used: The machine should be run at 
normal speed and voltage and a pair of volt- 
meter leads, separated a distance equal to the 
width of one commutator bar. placed on tin 
i ommutator under the center of one pole and 
moved from bar to bar to the center of the 
next pole of like polarity, the voltage at each 
Step being read. In this way the voltage 
between bars is obtained for a complete cycle 
ill) electrical degrees. 

Tile readings should be corrected tor meter 
constants and plotted as ordinates against the 
number of bars as abscissae, and a sketch 
showing the position of the poles should be 
made on the same sheet with the curve ob- 
tained. 



COMMERCIAL ELECTRICAL TESTING 



79 



Wave form on alternators is obtained by 
the use of the oscillograph, which is described 
under the heading; of electrical instruments. 



D.C. GENERATORS 
Preliminary Tests 

Preliminary tests on direct current gen- 
erators consist in drop on spool, polarity, hot 
and cold resistance measurements, air gap, 
potential curve, rheostat data, brush shift, 
running light and equalizing ring tests. 
With the exception of potential curve, 
rheostat data and equalizing ring, the tests 
have all been previously described. 

On all multiple wound armatures of self- 
contained machines not equipped with equal- 
izing rings, a potential curve must be taken. 
All the brushes except those on two adjacent 
studs are raised from the commutator, the 
voltage is raised to normal and the field 
current noted. This field current and the 
speed must be held constant for all other 
points on the curve. The brushes on stud 
No. 3 should now be lowered, those on No. 1 
raised and the voltage read between studs No. 
2 and No. 3. This procedure should be 
continued until voltage readings have been 



IUUU 








































/ 


/ 




900 






































,/ 


/ 








































/ 


/ 








800 


































/ 


/ 








































/ 


' 












^700 






























/ 


' 


















— 








































$600 




















































































§500 
$400 


















































































































































































\300 
§200 














































































































































































100 









































































































































/o 



20 30 

/4/nperes F/e/d 



40 



SO 



Fig. 19. Synchronous Impedance Curve on a 500 Kw., 600 Volt, 
360 R.P.M., 60 Cycle, 3-Phase. AC Generator 



taken between every pair of studs. The I 
should be made with the field current rising. 
The maximum voltage variation permissible 
is 4 per cent, of the average value. This I 
although similar in nature, should not be 



confused with the bar to bar potential curve 
taken to determine the wave Eorm of a direct 

current machine. 

TABLE VII 

Synchronous Impedance on a 500 Kw., 600 V.. 
20- Pole, 60 Cycle, 3-Phase Generator 



Amps. 




Amps. 
Field 




Arm. 


Field 


K P M 


224 


15.0 


I 1.9 


360 


260 


17.8 


13.7 


360 


300 


20.6 


15.8 


360 


352 


23 8 


18.3 


360 


398 


26 '.i 


20.7 


360 


474 


31.5 


24.5 


360 


180 480 

IS!) 


32.2 


24 8 


360 


.-, 1 8 


34.8 


26 7 


360 


557 


37.5 


28 2 


360 


7iH 


I7.ii 


36 I 


360 


7'. Hi 


52.8 


10.6 


360 


896 


59.5 


15.7 


360 


KM III 


66.5 


51 1 


360 



Equalizers consist of rings or cross con- 
nections tapping into equi-potential points on 
the winding of multiple wound armatures 
between each pair of poles. These rings pre- 
vent inequalities in voltage between brushes 
of similar potential, due to inaccurate center 
ing of tlie armature. The rings allow alter- 
nating currents to How from the stronger to- 
ward the weaker pole pieces, which slightly 
demagnetize the former and magnetize the 
latter, thus equalizing the voltage at the 
brushes. Not only do the tines prevent an 
interchange of heavy cross currents between 
brushes, but they also compensate for 
inequalities in magnetic pull at the pole pieces, 
tending to bend the shaft or overheat the 
bearings The tester should examine these 
rings to see thai the taps are equally spaced 
and all connections tight. 

If a machine has been correctly con 
nected, and there are no open circuits or 
ed spools in the field, the machine 
should build up when the field switch is closed 
and all resistance cut out of the field. If 
ii docs not, the resistance of the 1 1< 1. 1 should 
be cheeked with that oi a similar machine of 
the same size and voltage, as a 500 voll 
machine may sometimes b i tbled with 
a 250 volt held 

When .lulu uii j is had m building up the 

achine, it will usually bi fi und 

thai the currenl does no1 Mow through the 

field in thi direction ti i build up t he 

residual magneti m li eld switch 






GENERAL ELECTRIC REVIEW 



open, the residual flux gives a few volts on 

the armature and upon closing the switch the 
volta.L nearly zero, the field ter- 



















































|. 


















































L 
















































■< 


** 














































<* 












































pi 


S 














































2 














































'a 


/ 














































/ 


f 














































/ 
















































/ 
















































/ 














































, 


/ 
















































/ 
















































/ 




























































































































































































































































































/ 
















































/ 












































/ 




/ 


t 










































1 


' 




/ 












































/ 




/ 


















































1 














































/ 


















































f - 








































I 






, 






































\Ful/Load 





Amperes Mocfi/ne 



Fie. 20. Series Characteristic 



minals are connected t" the wrong brushes. 

'I'.. remedy, either reverse the field or shift 

the brushrs Over "lie pole. 

In locating the no-load electrical neutral on 
commutating pole machines, the fibre brush 
method is used. A fibre brush, provided with 

two nd terminals separated from 

one another by a distance equal t" the thick 

<>t "in' liar, is placed in a brush-holder on 

Stud. 'Idle brush is then shifted until 

zcr<> voltage is read between the two ■■ 
minals. The position oi the rocker arm is 
marked at this point. 'Idle fibre brush is then 
placed 'Hi ili' in-.' stud and the brushes 
shifted again until /.em voltage is obtained, 
this position of the rocker arm being also 
marked. This operation is repeated for each 
of the studs, the n>cker arm being finally 
■ in tin' mean of the positions previously 
marked. This setting locates the electrical 
neutral at ni 1 1' 'ad, which sin luld have the same 
position at full load. 

The shunt in the commutating ."'1..' field 
is then adjusted t<> give th< best commutation 
at full load, the amount of current shunted 
through the commutating pole field 1 



sured. The amount of this shunted 
cumin should always be recorded. 

Tin open circuit tests, already described, 
are sometimes taken on commutating 
pole generators. 

Tin building up of a series generator 
is a more complicated operation. Tlu 
load increases with the voltage and, 
therefore, great care should be taken 
in obtaining the correct external re- 
sistance to prevent the load from in- 
creasing rapidly. As it is practically 
impossible to decrease the external 
resistance enough (i.e., put the blade of 
the water box in far enough) to allow 
the generator to pick up. the usual 
method is to put the water box blades 
in and short circuit one of the boxes 
with a fuse wire and then close the 
circuit breaker and switches. If the 
machine then starts to pick up. and 
the voltage decreases as soon as the 
fuse wire bums away, there is too much 
resistance in the water boxes. They 
should therefore be salted (to decrease 
the resistance) and the operation re- 
.i ed. Should the resistance in the 
boxes be too small the load will in- 
crease very rapidly and the breakers 
may have to be opened to prevent 
the machine arcing over between 
brushes. 
After the brushes are set the german silver 
shunt should be adjusted to give the required 
voltage. 

A series characteristic is taken on all series 
wound generators. This is done by increasing 
the load by small steps until full load is ob- 
tained, amperes nne and volts machine being 
,uli step. The load is then 
reduced by small steps to no load, the same 
readings being taken. A curve is then pi 

res as abscissae and volts 
machine as ordmates (Fig. 20. 

In tlir case oi series machines which form 

: 1 ster sets, tin- guaram ; imes 

does not allow this curve to deviate by more 

than a certain percentage from a straight line 

Tin curve should be taken in all cases with 

erman silver shunt in place, if the lattei 

ary. 

e direct current generators are pro 

vided with collector rings for three-wire 

'ion. If there are two series fields, one 

should be connected in each side of the line. 

All other tests are made as on any direct 

current generator. If unbalanced readings 



COMMERCIAL ELECTRICAL TESTIXO 



81 



are required the compensator should be 

wired according to diagram. (Fig. 21.) 

A reading should lie taken at no load, 
normal voltage. With no change in the field, 
and holding constant speed, J load should be 
thrown on one side of the line and the voltage 
read from the neutral to each side of the line; 
volts and amperes line, volts and amperes 
field should also be read. One-quarter load is 
then put on the other side of the line, giving a 
balanced load, readings being taken as before. 
The load is then increased to A load on one 
side, this procedure being continued until 125 
per cent, balanced load is obtained, readings 
being taken at each step. Instructions some- 
times call for 50 per cent, unbalancing, in 
which case the load is increased 50 per cent, 
at each step instead of 25 per cent. 



Standard Efficiency Test 

The method of calculating efficiency by 
the method of losses is as follows: 

Consider a compound commutating pole 
generator. 

Let V L = Volts line. 

Cl = Amperes line = C a + C 9 = C,„+ C n 

C & = Amperes, shunt field 

C 4 = Amperes, armature = ( ' , f- C e 

C„ = Amperes, series field = ( '< ' , 

(K 8 + y<„) 

C\ = Amperes, german silver shunt = 
C L -C a 

I ,,, = Amperes, commutating pole field = 



ir, 



Cl~, 



Rn 



'(R,+ R 1B ) 

(.',, = Amperes, commutating pole ger 
man silver shunt = Cx.— C'„, 

A'. = Brush contact resistance 

K„ = Hot resistance of shunt held 

R t = Hot resi tance of armature 

A' 8 = Hot resistance ol serii s field 

A„ = Hot resistance ot series field german 
silver shunt 

A' l0 = Hot resistance of commutating 
pole field 

A',, = Hot resistance of C( 'lunulating 
pole field german silver ;hunt 

Then total CR drop ( \R t < \R t ■ ( ' R s 
<7v, ■ C l0 R lt ■ C U R U 



■Core loss watts, taken from the 
core loss curve corresponding to 
V L + CR for each load 

W 2 = Watts brush friction from core loss 
test. 



-vWVWSAA 



Slwnt' 
field 




Ser/esFif/d 



Fig. 21. Three-Wire Generator 

If the value taken from test appears incon- 
sistent, calculate W 2 by the formula: 

FxNxBxLxiix74(\ , 

\\ , = ' where 



13000 



F 



■ Circumference of commutator in 
feel 
N =R.p.m. 

B = Number of brushes 
L = Lbs. pressure per brush 
,« = Coefficient of brush friction for the 
particular type of brush used. 

In the case of engine-driven machines or 
those which are furnished without base, shaft 
or bearings, the bearing friction is omitted 
from the total losses, and is charged against 
t he prime mover. 

In nearly every ease it is preferable to use 
the calculated brush friction instead of thai 
obtained from test. During a shorl test, the 
commutator and brush contact surfaces can- 
not get into such good condition as thai 
which obtains after a long period oi com 
mercial operation. Consequently, the brush 
in. lion test does noi represent the conditions 
thai will exisl after the machine has been in 
operation for some time. The coefficienl of 
friction determines the value of brush friction, 
which in turn is determined by the condition 
.it the commutator and 1 iru sh c< mtad surface, 
This coefficienl varies considerably a1 firsl 
and only reac "ii tanl value al'tei a 

considerable period ol operation The 
eient used in the above formula for the cal 
culation of brush friction has been obtained 

b} mea haustivi ti on i i 

different types with various pressures and 
commutators. These tests extended over a 
n constanl and 






82 



GENERAL ELECTRIC REVIEW" 



TABLE VIII 
Efficiency and Losses of a 100 Kw., 525/575 V., Comp. Wound, 6-Pole. 275 R.P.M., D.C. Generator 



' i I-' 1 





IT) 


50 


7.-) 


L00 


125 


150 


Volts Line 


. 525 


53 . . 5 


551 1 


562.5 


.", , 5 


575 




Amps. Line . 


it 


13.5 


s7 u 




174 • 


217.5 




Amps. Shunt Field 


3.18 


3.25 




3.40 


3.4 




Amps. Ann 


3.1 


16.7 


90.3 


133.8 


177. 1 


22u.ii 




Amp lield . 




58 1 


87.6 


L16.8 


146 




Amps. Series G.S.S. 


U 3 


28.6 


12 9 


57.2 


71.5 




CR Drop 


.417 


.628 


12.1.-) 


1S.0 


23.9 


29.7 




E + CR . 


525.4 


543 8 


562 2 


580.5 


598.9 


604.7 




Core Loss 


1042 


1 124 


1 205 


1295 


1395 


14 25 




Brush Friction 


314 


314 


314 


314 • 


314 


3 1 1 




Bearing Friction 


— 


— 


— 


— 


— 


— 


— 


CR Armature 


— 


213 


7"7 


1750 


:;o.mi 


17711 




C 2 R Brushes 


— 


36 


135 


222 


33 1 


430 




CR Sliunt Field 
CR Rheostat 




1710 


1790 


1870 


1950 


1950 




CR Series Field 





33 


131 


296 


523 


S20 




CR ess. . 





16 


64 


144 


257 


in:; 




Total Losses. 


2986 


3.446 


1436 


5891 


7850 


10112 




Kw. Output 





23.4 


17. 8 


73.4 


100 


125 




Kw. Input 


2. '.19 


26.85 


52.24 


79.29 


107.85 


135.1 




% Efficiency 





ST. 2 


91.5 


92.6 


92 7 


92.6 




Brush Density 


— 


8.3 


16 05 


23.8 


31.6 


39.3 




Brush Contact Ri 


■S. 


ii pit;.-, 


in 1 1 


.01244 


.01055 


.0091 








Resistance Of Armature 25° C. .0893 ' Ihms, Warm .098 at 51° C. 

.it shunt Field 25 I 97.4 Ohms, Warm 105.3 Ohms at 47 

i oi Series Field 25° C 0358 I >hms, Warm 0386 ohms at 46° C. 

Series t'> S.S m, 9 ( Huns. 
Dimensions of Brushes 1J"X j>". No. of Studs 6. No per Stud 4. Coeff. of Friction = .2. 
Bru h Contact Vrea, One Side 5.625 Sq. In. Brush Pressure 1} Lbs. per Brush. 



TABLE IX 
Efficiency and Losses of a 70 H.P., 500 V., 6-Pole. 850 R.P.M.. D.C. Motor 



Vol1 Line 
Amperes Line 
Amperes Field 
Amperes Arm. 
CR 

E— CR . 
Speed 
■ I 

I i 

Bi ii ing Fri« I - 
CR Armature 
CR Bru.li 

CE Field 

:! I.' I I 

Kw Input 
Kw Output 

II P I Kltput 

1 
Brush Density 
Brush Contact Resis. 





500 


500 


.-,1 K i 


500 


500 






29 


5 s 


87 


116 


145 






2. 13 


2. 13 


2. 13 


2 13 


2.43 






26.5 


5.Y5 


si :, 


1 13.5 


l 12.5 






3 


6 


'.i 


12 


15 






197 


mi 


491 


188 


485 






2; 


2 175 


2450 


2400 


2350 




160 


160 


160 


li,n 


160 




530 




530 


530 


530 




63 


275 


638 


1150 


IS 20 




v 


36 


85 


153 


240 


. 121 5 


1215 


1215 


1215 


1215 


4. 75 


P. .MM 


5380 


5908 


i il i I :, 


14.5 


29 


i:; :, 


58 


72.5 


9.7 


21 


38 I 


r,j i 


65.9 




12.8 


32.1 


51 


70 


88 5 




67 


v' 8 


87.6 


89 s 


MILS 




5.15 


II 1.3 


1.-1.5 


20.6 


25.8 






.0178 





Ml 16 


nr;. 





Resistance of Armature 25 C 01 16 I >hms, Warm .0895 ohms at 50° C. 

Field 25°C 169 Ohms, Warm 191.5 Ohms at 60° C 
Dimensions ol Brush No. of Studs r, No. per Stud 3. H lbs. per Brush. 

Brush Coi One Side 5.62 Sip In. 



COMMERCIAL ELECTRICAL TESTING 



83 



factory conditions for both brush and coi 
mutator surface. The resulting values oi 
brush friction can, therefore, be relied on to 
give accurati' and final results. 

11 3 - Bearing friction from core loss test 

Wb = Watts output -i I | 
The brush contact resistance, A', is that taken 
from a curve made for different types of 
brushes, and corresponds to the brush current 
density per square inch at any given load. 
Brush current density per square inch = 

<\ 
'. total brush area 

One-half the total brush area = 

where /= Length of brush parallel to the shaft 
it' = Width of brush 
5 = Number of studs 
t = Number of brushes per stud. 

For reasons similar to those just given, 
extensive tests have been made to determine 
the contact resistance of different types of 
brushes, from which curves have been plot led 
with brush current densities as abscissae and 
either brush contact resistance per square inch 
or CR drop in brush contact as ordinal es. 
In order to measure the contact resistance 
directly the commutator would have to be 
short circuited and the voltage drop measured 
from the commutator to the surface of each 
brush. This would be a long operation en- 
tailing considerable expense. The results also 
could not be reliable owing to the newness of 
commutator and brushes. It is therefore 
preferable to use the brush contact resistance 
obtained from the curves mentioned. 

It H 3 = bearing friction from core loss test, 
then total loss in watts = IW = W \+ W ' t -i 11'., 

: 4 »^+cyfr,+ c , ,*j?,+ (CiV i <;-/<„) + 

The quantity C a Ib, -C t 2 R t = C 2 R loss in the 
shunt field rheostats. 

The watts input 11',, will then I i 

W a = W b + IW, where II',, -waits output 

=c L v L 

w„ 



The efficiency E = 



II' 



In case a core loss test is not made, the 
running lighl i^ substituted in the formula for 
the quantity ill', • W t -\ ll'.,i. If the segre- 
gation of the losses iii the series and commu- 
tating pole fields and their res] ective german 
silver shunts is nol required, th' resistances 
A„ and A'„ may be combined to equal Rsp, 
likewise A',,, and A',, to equal Rep. 



The total losses will then be 

SW= Running light I (',-A, • < r 'A, 
<-'„!'/.+ C L 2 Rs f ■ C L 2 Rc P . 



so 

30 
70 

.i 
.£ so 

so 

20 

/O 

O 



....i::::::::::::i::::i: 


^4r~l ■& *. ""> * 


=--t=i!===:)===:J:===: :EExI=E 


r" V. ; 




1_ 


t 4^X X XXX 


i : 


X X 


X , L 


t 


■■• 








1 i 1 



60 SO 




60 80 



/20 



/40 



Fig. 22. Efficiency and Losses on a 100 Kw„ 6 Pole, 275 R.P.M. 
5;5'575 Volts, Compound 'Wound DC. Generator 



To calculate resistances ho1 when calcula- 
ting efficiencies, the temperature should be 
i ibtained from t he formula: 

T — (K X rise by thermometer) I -">° C. 

K is the rati" between the rise in temperature 
by thermometer and thai determined by 
resistance measurement. Resistano 

;il li -I I 'in have been deter- 

I by actual tests on a large number oi 
different armatures and fields. for all anna- 
lures, or field spools of revolving field ma 
chines, K" — 1.25. For stationary ventilated 
field .pools A' I 7 See Tables VIII and IX. 
and Fig, 22 for form used in calculating and 
plotting efficiency. 



84 



GENERAL ELECTRIC REVIEW 



A FINANCIAL STATEMENT OF THE CAUVERY 
HYDRO-ELECTRIC DEVELOPMENT 




Dewan L. Ananda Dao 



In the January issue of the Review, we 
printed a description of the Cauvery Hydro- 
electric development in India the first 
enterprise of the kind of any importance to 
be undertaken in that country, and as such, 
it testifies to the force of character and 
progressiveness of His Majesty, The Ma- 
harajah, and his 
able administra- 

Since the pub- 
lication of this ar- 
additional in- 
■11 has been 
r e c e i v c d which 
adds materially to 
the interest of the 
subject. As stated 
in the former ar- 
ticle, the develop- 
ment was under- 
taken for the pur- 
pose of supplying current to the Kolar gold 

i'ti. London agents of which are M 
John Taylor & Sons, to whose foresight and 
co-operation the enterprise largely owes 

■ 5S. 

('urn ui is also transmitted to the cities 
of Bangalore and Mysore, for lighting, etc. 

The origi- 
nal develop- 
ment 

ted 6000b. p.; 
to this was 
added l v ■ 
tensions of 
5000 and 2000 
h.p. respec- 
tively, mak- 
ing in all 
I SHOO h.p. 
By the origi- 
nal arra 
ment, the 
mining com- 
panii 
to p a y in r 

power a flat 
rate based on 
the nor 
full load con 
sumption of 
the motors, 
the agree- 



ment covering a period of ten years, and the 
amount per horse-power varying according 
to the following sliding scale: 

1st year £29 per h.p. yr. 

2nd, 3rd and 4th years £18 per h.p. yr. 
5th year up to £24 per h.p. yr. 

5 years following £10 per h.p. yr. 

During the first year the 
actual payment for the 
power was £18 as in the 3 
years following, the £11 
being added for the pur- 
pose of reimbursing the 
Government for the cost 
of the distribution plant. 
When the second installa- 
tion was made, the mines 
installed their own distri- 
bution plant and paid £18 
per h.p. year for power; 
with the third installation, 
the rate became £10. 
The total capital expend- 
ed by the Government in the development has 
been §2,500,000. The gross revenue received 
overaperiod of 6; 3 4 years has been S3, 743, 000. 
The expense of operation and maintenance 
has been $703,000. The net revenue, against 
capital of 82,500,000, is therefore $3,040,000. 




John Taylor. Head of the 

Firm of John Taylor 

■-& Sons, London 




85 



A MOTOR OPERATED RAIL MILL 

By B. E. Semple 

Chicago Office, General Electric Company 



~T-.' : 



The rail mill at the new works of the 
Indiana Steel Co. at Gary, Indiana, has a 
capacity for rolling 166 tons of finished 
rails per hour, and is the largest and most 
modern mill of this description in the world. 

This mill not only has the 
distinction of containing the 
largest induction motors ever 
built, but of being the only 
rail mill in existence entirely 
motor operated in which finished 
rails are rolled direct from the 
ingot without reheating. 

Some 30,000 rated horse-power 
in alternating and direct cur- 
rent motors are required for 
the operation of the mill ; about 
25,000 horse-power being fur- 
nished by alternating current 
machines and the remainder 
by direct current. The main 
rolls are driven by six induc- 
tion motors rated as follows : 

Two 1-14 pole, 2000 h.p., 2] I 
r.p.m., 6600 volts, 3-phase, 25 cycles, 
Form M. 

One 1-40 pole, 6000 h.p., 75 
r.p.m., 6600 volts, 3-phase, 25 cycles, 
Form M. 

One 1-36 pole, 6000 h.p., S3 r.p.m., 
6600 volts, 3-phase, 2.5 cv cles, Form 
M. Fig. 1. 

One 1-44 pole, 2000 h.p., lis 
r.p.m., 6600 volts, 3-phase, 25 cycles, 
Form M. 

One 1-34 pole, 6000 h.p., SS r.p.m., 660(1 volts. 
3-phase, 25 cycles, Form M. 

All of these motors are direct connected 
to the roll machinery through couplings of 
the flange type, which are constructed of 
steel. The motors are located in a room 
adjacent to the mill propei and cannot be 
seen by the operators manipulating the st< i I 
being rolled. 

Fig. 1 is a view of the two 1 1 pole. 2(11)1) 
h.p., 214 r.p.m. motors, each of which 
operates a two-high blooming mill, these 
motors being installed in a room on the 
opposite side of the mill from the other four 
motors. 

These two motors are of the slip ring type 
and are rated at 2000 h.p. each, at -10° C. 
rise; 25 per cent, overload continuously 
at 50° C. rise, and 50 per cent, overload 
one hour at 60° C. rise They have an 



equivalent break down torque of 6800 
h.p. The bearings are water jack 
and are made of cast iron with babbitl 
lining, each being 24 in. diameter. Ill) in. 
long. 




2000 H P.. Three-Phase Induction Motor Geared to 
Two-high Blooming Mills 



The revolving element, including the fly- 
wheel, has a WR 2 value of 4.720,000 pounds 
at one foot radius. The flywheel is made 
up of steel sections, or laminations; it is 
17 feet in diameter and weighs 50 tons. 
Each motor complete weighs I'.is tons, 

Both of these motors were assembled and 
tested at the works of the General Electric 
Company before shipment, only the fly- 
wheels being assembled at the point of 
installation. These wheels are 17 feet in 
diameter and have a peripheral speed at 
synchronous motor speed of 11120.11 feet 
per minute, which fact readily explains the 

ity for constructing them of 
laminations. The laminations are firmly 
held together by very heavy rivets passing 
igh tli< wheel at righl angle to its 
diameter, and are attached to a steel hub 
which is double keyed to the shati 



86 



GENERAL ELECTRIC REVIEW 



Each motor is provided with a thrust 
biaring or mechanical fuse, mounted on 
the from pedestal and held in place by two 
breakable rods which can be seen in the 
illustration. The purpose of this thrust 
bearing is to care only for ordinary thrusts 
in amounts less than 150 tons. This point 
may be exceeded at times, however, by the 
breaking of a roll or a roll spindle, and in 
such emergencies the thrust is sufficient to 
break the rods holding the collar in place. 



gear arranged to give six revolutions per 
minute on the first two passes and ten 
revolutions per minute on the next two. 

A short shaft mounting a pinion is coupled 
To the motor shaft. This pinion engages 
with a large gear mounted on the intermediate 
shaft, which also carries a double faced 
pinion, each face engaging the large gears 
on the roll shafts. 

This gearing is of special interest when 
the speed ratios and the power transmitted 




Fig. 2. 6000 H.P., Three-Phase Induction Motor. This motor drives three stands of rolls, one 
of which takes three passes, and the other two one pass each 



thus allowing t lu- rotating element to move 
longitudinally away from the rolls, there 
by relieving the thrust and preventing 
further damaj oil machinery or 

to the motor itself. The brush rigging is 
arranged in such a manner that it can move 
tudinally with the rotating element. 
thus allowing the brushes to remain on the 
collector rings regardless of the position 
of the rotor. 

These two motors operate the first four 
"pass. i driving two stands 

of I- in. blooming mils. They are connected 
to the rolls through a double reduction 



are .considered. In one case the motor 
driving pinion has a 21 in. face, 23 teeth, 
and a pitch diameter of 26^ in; the large 
gear engaging this pinion has a 21 in. face, 
135 teeth, and a pitch diameter of 12 feet, 
ln'\ in.; and the inter pinion has 

a 27 in. face, 2(i teeth and a pitch diameter 
; 21 in. The gears on the roll shafts 
are each of IS feet 5| in. pitch diameter. 
27 in. face, and contain llti teeth 

The ingot which weighs about MIDI) poundf 
and measures about 65 in. long. 24 in. wide 
and 21) in. thick, is received from the reheat- 
ing furnaces at the first pass on a motor- 



A .MOTOR OPERATED RAIL .MILL 



87 



operated roller table and, after passing 
through the four passes operated by these 
two motors, is reduced to a piece L83.6 
in. long, 14.5 in. wide, and 11. 5 in. thick. 
As previously stated, the other four large 
motors are located in a room on the opposite 
side of the rail mill proper, being separated 
from it by a brick wall as in the case of the 
two 2000 h.p. motors. 

The rolling operation is now taken up 
by the 40 pole, (5000 h.p., 75 r.p.nt. motor, 
which is direct connected to a 40 in. three- 



This motor has the same overload ratings 
as those previously described and an equiv- 
alent breakdown torque of 1.6,500 horse power. 

It was found that this motor was too 
large to be shipped even partially assembled, 
and as a result it was entirely assembled 
at the point of installation, the stator punch 
ings and windings and the rotor punchings 
and windings all being put into place during 
the const ruction process, expert core builders 
and winders being senl from the works to 
carry on the wi irk. 




Fig. 3. Finishing End of Rail Mill 



high mill through which five passes are made. 

This motor differs somewhat in construc- 
tion from those just described, and in addition 
to being larger in horse-power and slower in 
speed, obtains its flywheel effed of LI, I on, do 
i1 -me foot radius by Li ing its flywheel 
mounted directly on the spokes of the rotor 
as shown in illustration on pa-e 50 

The bearings for this motor are :;u in 
diameter and 70 m. long, water jacl 
and babbitt lined. The stator frame is 28 
feet in diameter outside and arranged in 
four sections; the rotating elemenl being 
L'l feet in diameter and the weigh! of the 
motor complete 392 tons. 



on November 29th, L908, the switches 
controlling the lines to this motor were 
closed', and the motor was started and opera 
led at tull speed for the fii iince thai 

date it has been in regular operatii m. 

Two trials wen in starting the 

mi-:, ir; 'Mi the lirsl trial tin una. u wa 
brought to aboul hall speed when, due t" 
a large volume of smoke issui m the 

en es, the switches had to !»■ opi ned 
and investigation n ■■ ealed lamp 

earl". n lodged among the grids in such a 
tie section of resistance was 
overheated. This trouble being rem 

ml. 



S8 



GENERAL ELECTRIC REVIEW 



In starting one of the other motors, two 
trials were also necessary, the first being 
unsuccessful due to a broken resistance 
grid. 

The steel makes five passes through the 
stand of rolls driven by this motor, three 




Fig. 4. Primary Control for Three 6000 H.P. Induction Motors 



of them being in the same direction and on 
the same level as that corresponding to the 
fourth pass, and two in the reverse direc- 
tion; the mill being three-high, thus allow- 
ing the motor to operate in the same direction 
continuously. 

The fourth motor in the cycle of operation 
is a 36 pole, 6000 h.p., 83 r.p.m. machine, 
which is also direcl connected to its work 
and differs only slightly from the 6000 h.p., 
75 r.p.m. motor jusl described. This motor 
is shown in Fig. 2. It has a total weight 
of ;i7t ions, with a flywheel effect of 
10,330,000 lbs. a1 one fool radius, the equiv- 
alenl break down torque being 18700 horse- 
power. It was also shipped disassembled, 
its proportions bring such as not to admit of 
even a panial assembly at the works. 

The steel makes five passes through three 
stands of rolls driven by this motor, the 
stand next the motor coupling being three 
high and taking three of the passes, the 
two additional stands each taking one 
pass. 

The fifth motor in the chain is a 44 pole, 
2000 h.p., 68 r.p.m., machine. This is the 
slowest speed motor in the mill and has 



practically the same overall dimensions as 
the 6000 h.p. motors. It has a total weight 
of 289 tons, a flywheel effect of 7,500,000 
pounds at one foot radius, and an equiv- 
alent break down torque of 5050 horsepower. 
This motor drives one stand of rolls through 
which the thirteenth pass is 
made, the stand being only 
two-high. 

The sixth and last large 
motor in the chain is a 34 
pole, 6000 h.p., S8 r.p.m. 
machine having the same 
overall dimensions as the 
other two 6000 motors. Its 
total weight is 374 tons, its 
flywheel effect 10.330.000 
pounds at one foot radius, 
and its equivalent break 
down torque 20600 h.p. 

Three stands of rolls are 

driven by this motor through 

which the 14th, 15th and 18th 

ses are made, all three 

stands being two high. 

The conversion from ingot 
to finished rail is accom- 
plished in is passes by these 
six large motors, tin com- 
plete cycle for one ingot re- 
quiring a trifle more than 357 seconds. 

This does not mean, however, that the 
six motors in the chain are loaded for only 
a short portion of the time extending over 
357 seconds, as ingots are being started on 
their journey almost as fast as they can be 
brought up to the first pass from the reheat- 
ing furnaces. In rolling 166 tons per hour 
an ingot is started through the mill every 
90 seconds. 

After the steel has completed the 18th 
pass, and is cut into lengths by the hot saws. 
it passes through the cambering machine, 
which is driven by a 4 pole. 40 h.p.. 750 
r.p.m.. 440 volt induction motor of the 
squirrel cage type, and on to the finishing 
department to be straightened and drilled: 
this work taking place after the rails have 
entirely cooled off. 

The straightening presses, of which there 
are eighteen, are each driven by a 4 pole, 10 
h.p., 750 r.p.m., squirrel cage type m >tor 
equipped with a high resistance rotor, the 
object of this high resistance being to increase 
lip at full load, thus allowing the flywheel 
with which each press is equipped to become 
effective and to assist the motor in its work. 



A .MOTOR OPERATED RAIL MI I.I. 



89 



After the rails are straightened they are 
drilled by motor operated drills of which 
there are eighteen, each drill being driven 
by a 4 pole, 10 h.p., 750 r.p.m., 440 volt 
squirrel cage type motor which is a duplicate 
of those on the straightening presses, except 
that they are provided with standard low 
resistance rotors. 

Fig. 3 is a general view in the finishing 
department, the rail drills being on tin- 
left and the straighteners on the right. 

The apparatus for starting, stopping and 
controlling the six large motors is of special 
interest, inasmuch as it contains certain 
new features which were necessary in the 
operation of motor driven rolls to obtain the 
best results. 



reversing switches, making it impossible to 
operate the latter while the main switch is 
closed. The reversing switches are also 
interlocked as regards each other, to prevenl 
both being closed at the same time. 

Tin' main line oil switch is automaticallv 
opened in cases of overloads or short circuits. 

The secondary cunt ml consists of iron 
grid starting resistances with contact or 
panels and notching up and down relays, 
the latter being shown directly at the 
left of the contactor panel in Fig. .">. 
The starting resistances are mounted in 
frames on the floor behind the contactor 
panel. 

The regulating device mounted on the 
relay panel controls the opening and closing 




Fig. 5. Secondary Control for 6000 H.P. Induction Motor 



Fig. 5 is a general view of the secondary 
control apparatus for one of the (iOOO h.p. 
motors, and Fig. 4 shows the primary 
control for three motors. 

Each motor is controlled by a master 
controller located in the operating pulpits 
in the rolling mill, the remainder of the 
apparatus being placed in the motor room 
near the motors. Provision is also made 
for operating the motors from the secondary 
control board in the motor room, if found 
necessary. 

The primary control equipment for each 
motor consists of one motor-o| erated three- 
pole line oil switch, two solenoid operated 
reversing switches, the necessary relays, 
and indicating and recording instruments. 
The main oil switch is interlocked with the 



oi the contactors, and in addition to perform 
ing the function of energizing the eontactor 
magnets during the starting operation, also 
opens ili'- contactor circuits at the proper 
time to c< 'in rol t he slip. 

Tit'- controlling device once properly ad- 
justed is entirely automatic. When the 

load increases, proportional resistance is 
automatically connected into the secondary 
circuit, increasing 'lie slip and allowing the 
flywheel t" share the load with the motor. 
As the load decreases, the slip is reduced and 
the motor restores energy to the flywheel 
in preparation for the next peak load. 

'I'll.- net resull "t this method "t control 
is to greatly smooth ou1 the peaks which 
would otherwise occur in the load curve at 
every pass. 



90 



GENERAL ELECTRIC REVIEW 



The control equipment is operated by 
direct current at 250 volts, and in the event 
of failure of either the direct or the alternat- 
ing current supply the apparatus is auto- 
matically protected. 

The rotors continue to revolve for a long 
period after power is shut off, on account 
of the large flywheels. When, due to accident 
or other causes, it is necessary to stop the 



was opened; the 6000 h.p., S3 r.p.m. motor 
operated for one hour and thirty-seven min- 
utes under the same conditions; while with 
direct current applied to one phase immed- 
iately after opening the line switches, the ro- 
tors ceased to revolve in less than three minutes. 
Two 10,000 kw., 6600 volt circuits from 
the power station supply the six large motors, 
one circuit feeding the two 2000 h.p., 214 




Fig. 6. Aluminum Cell Lightning Arresters 



motors quickly, direct current is admitted 
to the stator windings through external 
resistance, the rotor windings meanwhile 
short circuited. Suitable oil switches 
interlocked with the main line switches are 
provided urrent 

power circuits to the stator windings. On 
one occasion one of the 2000 h.p., 211 
r.p.m. motors continued to revolve for a 
i of two hours after the main line switch 



r.p.m. motors and the 6000 h.p.. ?."> r.p.m. 
motor, the other circuit feeding the remaining 
motors. One additional circuit enters the 
mill and supplies power through motor- 
generator sets to the direct current system 
for the various direct current motors used 
rani s and tables. 
All three of these circuits are protected 
against lightning and surges by aluminum 
cell arresters, which are shown in Fig. 6. 






91 



SOME POINTS OF MODERN PRACTICE IN INDUCTION 
MOTOR CONSTRUCTION 

By E. L. Farrar 



Modern practice in induction motor con- 
struction is toward the elimination, so far as 
is consistent with good engineering, of inactive 
material; this inactive material being largely 
confined to the stator casting, bearing 
brackets, and the base or rails. 

Inasmuch as the designers are rather 
limited in the matter of distribution of metal 
in the bearing brackets, but little elimination 
of weight can be made there except at the 
expense of rigidity. Two rails may be 
substituted for a base, and a saving made 
there if thought advisable; but the stator 
frame affords the best opportunity for the 
elimination of weight without a sacrifice of 
rigidity, at the same time providing for the 
most efficient heat radiation. 

This idea in induction motor design has 
been worked out very carefully m the riveted 
frame construction of the smaller and the 
skeleton frame in the larger sizes of G.E. 
induction motors. 

The use of straight versus overhung slots 
in the stator punchings has been open to a 
great deal of discussion. While given values 
of efficiency and power factor may usually be 
obtained with the use of less active material 
(i.e., laminations and copper) if overhung 
slots are employed, the difficulties in ade- 
quately insulating the windings with this 
construction and of making repairs render 
the use of straight slots desirable in all 
except the small sizes, even at the expense 
of increasing the amount of active material 
for a given size of motor. 

In the small sizes, if the lesser insulation 
inherent in overhung slot construction is not 
sufficient, as might be the case, for instance, 
where strong acid fumes an: prevalent, it is 
often preferable to use a totally enclosed 
motor with overhung slots, it being so much 
easier to maintain good characteristics in 
these sizes with this construction than with 
straight slots. 

With the increase in the general use of 
electric drive, a greater variety of conditions 
under which motors have to operate must be 
, This has led to the gradual Lmprovemenl 
in the character of insulation Often in 
small motors where overhung slot are usually 
used, the whole stator is dipped many times 
in heavy insulating compound and baked 
several hours in a high temperature. This 



compound thoroughly impregnates the entire 
winding, cementing the wires together and 
making the machine moisture proof. 

Where straight slots are used, the s1 
coils can, of course, be thoroughly insulated 
before being placed in the slots. Except 
wffiere small wire is used, it is considered 
better practice to wind the coils on forms 
which give them the exact shape and dimen- 
sions required, rather than wind them on a 
straight form and then pull them in shape. 
The coils are pressed in hot moulds to 
remove any high spots that might be subject 
to undue pressure when inserted in the slot. 
This moulding also melts and fills the coil 
with cement, binding the layers together. 
After being moulded, the coils are thoroughly 
insulated all over, the slot portion having an 
extra heavy re-inforcing. The coil is com- 
pleted by being dipped many times in heavy 
insulating compound and baked several 
hours at a high temperature. 

There is still some diversity of opinion 
among manufacturers as to the proper 
construction of squirrel cage type motors, 
but experience shows that for the smaller 
sizes a better electrical joint can be obtained 
by the use of soldered end rings, while for the 
larger sizes, a bolted construction, using 
spring washers to compensate for unequal 
expansion of the bars and bolts, is the most 
suitable. 

The air gap of any induction motor is of 
necessity relatively small, and experience 
shows that for all except the smaller sizes it 
is important to have a means of centering the 
rotor in the stator when the wear on the 
bearings becomes pronounced. In order thai 
the rotor may be centered accurately, it is ol 
course necessary that a gauge be furnished 
with each motor by the manufacturer. 

Exhaustive experiments have 1. 
ducted to determine the best friction ; 
to use for induction motor bearing lin 

■ hi the resul; 
years of experience in building indu 

i be little quesl I m bu1 
thai casl iron shells lined with hard o 
called tin babbitl a ; "'st for all i 

the smaller motors. For these an all 
used thai lias the same desirable qu 
inherent m babbitl :vi;.. thai ol nol scorin 
shaft in case t he bearing freezes I hn iu 



92 



GENERAL ELECTRIC REVIEW 



proper lubrication. All bearing housings 
should be made dust-proof. 

Although some manufacturers still furnish 
rails instead of a sliding base, the majority 
of engineers agree that a universal base, 
which can be used for floor, wall or ceiling 
mounting, is superior to either rails or 
separate bases for floor and ceiling suspension. 
In order that the belt may run true on the 
pulley, the base should be designed to prevent 
the belt tension from pulling the motor out of 
line. Also, there are a great many advantages 
in having a universal belt tightening screw 



that moves the motor both ways on its base: 
the base being interchangeable end for end, 
thus permitting the tightening screw alwavs 
to be located on the front side of the ma- 
chine away from the belt. 

The above is a brief outline of modern 
practice in induction motor construction. 
Improvements are continually being made, 
but they usually relate to details that have 
not been mentioned. The fundamental 
ideas in the construction of these motors have 
been so carefully worked out that the)' have 
proved highly satisfactory in operation. 



SEWING MACHINE MOTORS DRAWN SHELL TYPE 

By R. E. Barker 
Small Motor Department 



In 1845, Howe produced the first satis- 
factory sewing machine, and since that time 
vast numbers have been made and marketed 
for many varied purposes. This invention 
has perhaps done more to lighten the labors 



times dangerous fatigue engendered by the 
long continued pumping action of the feet 
upon the sewing machine treadle. .Many are 
the auxiliary devices proposed to avoid this 
laborious operation of foot power supply, but 



6 -.-■■■S - ■ 

Switch 

Bracket 

Base 

date 

/faisec'Tae/e 




Fig. 1. Form H Motor Attached 

of the housewife than any uther, and the 
greatest number of machines sold haw- been 
those designed for household use. 

However, with the advantages of con- 
venient, uniform, and rapid sewing by ma- 
chine, there comes the unpleasant and some- 



to High Arm, Drop Head Machine 

among all of these the modern electric motor 
of small size, comparatively easy application, 
and reasonable cost, is undoubtedly the : 
favored in all dwellings where electric power 
is available. 

To meet the demand for a motor for this 



SEWING MACHINE MOTORS -DRAWN SHELL TYPE 



u:; 



service, the General Electric Company has 
recently perfected a new design, in which the 
drawn shell type of construction is employed. 

These sewing machine motors are adapt- 
able to all standard sowing machines of either 
stationary or drop head style havingthe hand- 
wheel in the usual position. It is unnecessary 
to disturb any part of the sewing machine to 
attach the motor; hence in case of failure of 
electric current, or removal to a locality where 
electricity is not available, the belt can be 
attached immediately and the machine opera- 
ndi by foot power. 

A noticeable feature of the equipment is 
the ease with which the motors can be 
attached to or removed from the sewing 
machine by persons possessing but slight 
mechanical skill. 

This motor marks a long step in advance of 
the sewing machine motor formerly sold by 
the Company. Its design is such that by 
using only two forms it may be applied to 
substantially all types of stationary and 
drop head machines; thereby obviating the 
necessity for special attachments for each 
make of sewing machine, as heretofore. 

The belt tightener and other accessories 
used with the superseded line of motors have 
been entirely eliminated, and the motors now 
offered are self-contained in every particular, 
the outfit including snap switch, connecting 
cord, etc., etc. 




Fig. 2. Form K Motor Attached to Low Arm Machine 

Pig. 1 shows an alternating curreni motor 
assembled upon a high arm drop head sewing 
machine; Figs. 2 and .". show a low arm 
sewing machine fitted with a ! /30 h.p. new 
type of motor. 

Thf Form K outfil is designed for the low 
arm or automatic types of sewing machines, 



and for the high arm machines where the 
Form II motor cannot be used owing to 
peculiarity in head design. 



■ Rocker Levers 



Or iv inn Pulley 
\ 




End View of Form K Motor Attached 
to Low Arm Machine 



Complete outfits are comprised of the 
following parts : 

Form HC or H. One motor complete with 
bracket and base; one bobbin winder; one 
treadle pull; one leather and one rubber 
belt ; one ornamental cover; one screw-driver; 
and four wood screws (Fig. 4). 

Form KC or K. One motor complete with 
bracket, levers and base; one treadle pull; 
one leather driving belt; one rubber belt; one 
ornamental cover; one screw-driver; and four 
wood screws (Fig. 5). 

Family size sewing machine motors are 
built in the following sizes, for the frequencies 
and voltages listed: 

ALTERNATING CURRENT 60, 40 and 25 Cycles 







- 




S 


Al'I'kOX. \\T IN LBS. 


11 1' 


4» >. - u 


Net 


Shipping 




mil u 


> 


Form 














lie 


I.' 


II. 


KC 


D>S 


I 30 


l SI ii i 


60 


1 in 


19 


IN 


;:n 


29 


DSS 


30 


LSI ill 


mi 


220 


1!) 


l.s 


30 


29 


DSS 


l 30 


2400 in 


1 lo 


Ill 


IS 


30 


29 


DSS 


1 30 


2400 4H 


120 


19 18 


:;n 


L".l 


DSS 


I :;n 


2400 in 


220 


l!l 18 


::u 29 


DSS 


1 in 


i: 25 


l in 


III IS 


30 "i 


DSS 


i in 


1500 


25 




in 


IS 


:;n 


29 



CONTINUOUS CURRENT Shunt Wound 



Type 


ii i- 






APPROX, 


WT. IN LBS 

Shipping 




II 


K 


! - "rm 
11 K 


DSD 
DSD 


i .m 
i 30 


I7IIO 

171 in 


110 

L'L'O 


ID 
Ill 


l.s 
IS 


:;n _»i 
;:ii I'll 



94 



GENERAL ELECTRIC REVIEW 



Full and clear instructions for assembling 
are shipped with each out lit . When the outfit 
has been installed in accordance with the 
directions and the motor connected to the 




When it is desired to lower the drop head 
or place the box cover on a stationary head 
sewing machine, the motor may be turned 
on its swiveling base plate or may be removed 
entirely from the machine. Thus the 
motor, when not in use, may be protected 
from dust, etc. Fig. 6 shows the appear- 
ance of the same sewing machine as that 
illustrated in Fig. 1, when the motor is 
removed and the drop head closed. 

Sewing machine motor drive is one of 
the most attractive applications of 
fractional horse-power motors ever made 
by the General Electric Company. Large 
numbers of the earlier type with separate 
belt tightener have been sold, and now 
that a more improved, complete, self 



Fig. 4. Form H Motor 

source of electric supply by means of the 
flexible cord and plug, the operator can start 
the machine by turning the snap switch and 
after govern the'speed to a nicety by 
gently increasing or diminishing the pressure 
of the fool i >n t he treadle. 

Pressure of the foot releases the brake and 
tightens the bell by means of the driving 
pulley, thus starting the machine or increasing 
the speed. Redu tion ol pressure on treadle 
us the belt and decreases the speed. 
To stop machine quickly, remove all pressure 




Fie. 5. Form K Motor 



the treadle and the brake will be auto- 
matically set against the handwheel, bringing 
the needle i'. rest immediately. Tins method 
of control is simple and sat: ; tin' 

speed of tlie sewing machine may be regulated 
quickly to suit the varying requirements 
of different classes of w<>rk. 




Fig. 6. Drop Head Machine Showing 
Motor Removed 



contained, lighter and more efficient 
motorisoffered.it is confidently expected 
that the demand will greatly increase 
\\ hen its several good features become 
known to the purchasing public. The 
new motor is much cheaper to operate 
than the old, actual tests showing a 
saving of 50 per cent, in the current 
bill. The power used is about equal 
to that taken by one sixteen candle- 
power incandescent lamp. This fact 
should make the new outfit especially 
attractive. 
For strength, reliability, simplicity of 
application and facility and economy of 
operation, these outfits leave nothing to be 
desired, and persons having once tried this 
method of drive find it absolutely indis- 
pensable. 



95 



OIL AND TRANSFORMER DRYING OUTFITS 

By E. F. Gehrkexs 



Experience has shown that it is practically 
impossible to prevent moisture from being 
deposited in transformers during transpor- 
tation or storage, condensation taking place 
on the surface of the oil as well as on the 
metallic surfaces whenever these are cooler 
than the surrounding air. It is therefore 
important, especially with high voltage trans- 
formers, that considerable-' attention be given 
to the matter of drying out the transformer 
itself, as well as the oil to be used. A 



provided, one at the top of the furnace for the 
admission of fuel, and one at the bottom for 
removing the ashes ami also for regulating the 
draft. Wood and charcoal have been found 
from experience to give good results as fuel. 
Hard coal may also be used, in which case 
it may be necessary to use forced draft, 
which can easily be obtained by tapping the 
pipe between the blower and the furnace. 
Standard 3 in. wrought iron piping, which 
is procured almost anywhere, is used through- 




Fig. 1 



portable oil and transformer drying outfit 
suitable for this purpose has therefore 1 em 
developed, which will be briefly described 
in the following paragraphs. 

The outfit consists of the following parts: 

Hot air furnace, 

Positive pressure blower, 

Dust collector, 

Driving motor. 

Necessary piping, pulleys and belt. 

The outfit is shown diagrammaticallv in 
Fig. 1. 

Hot Air Furnace 

This furnace contains a A in. wrought iron 
coil suitably mounted inside a sheet iron 
casing, the latter being fastened t" a :as1 iron 
base. The furnace is designed in a manner 
similar to a self-feeding stove. Two doors are 



out the outfit; the connection between the 
blower and the furnace is. however, senl 
with tin' outfit. If the connections betwi 
the furnace and the transformer lank are of 
appreciable length it is advisable to have them 
covered with suitable heat -insulating mate- 
rial. Common stove pipe may be used for 
leading the smoke from the furnace to the 
open air. 

Positive Pressure Blower 

The blower is of the ordinary positive pres- 
sure type and should !»• rotated in such a 
direction that tin- air will he pulled in through 
the dusl collector, it has a normal cap icity 
■ >f :;ni] cubic feet of tree :m- i"i- minute, 
delh -red at a pressure "t 6 He per squ 
inch, ami is designed for a i 600 

r.p.m., requiring L5 h.p. when delivering 
normal output . 



96 



GENERAL ELECTRIC REVIEW 



In case the outfit is used for drying trans- 
formers only, smaller pressure is required and 
a 5 h.p. motor will be sufficient. 

Dust Collector 

The dust collector, or air filter, is of very 
simple construction and is attached to the 
inlet of the blower. It consists of a pipe 
4$ in. in diameter, made from perforated 
sheet metal and connected to the blower with 
a suitable elbow. Cheese cloth should be tied 
around this pipe so that when the outfit is in 
operation the air must pass through the cloth, 
thereby being effectually filtered. The cloth 
must, of course, be changed front time to time. 

Driving Motor 

Any available driving power, be it from a 
steam engine, gas motor, electric motor, etc., 
may be used for driving the blower. The 



pulleys of the blower and motor should be of 
such a ratio as to drive the blower at the 
required speed of 600 r.p.m. 

Piping, Etc. 

In making up the pipings between the 
furnace and the oil tank, it is necessary 
to extend this pipe above the oil level, so as to 
prevent the furnace from being flooded with 
oil in case the motor is stopped and the valve 
at the base of the tank is not closed. 

Weights 

The net weights are as follows: 

Hot air furnace . . . 1250 lbs. 

Blower 800 lbs. 

Dust collector and piping . 1.30 lbs. 

Total .... 2200 I 



OBITUARY 



John Trumbull Marshall, assistant engineer 
of the Lamp Works of the General Electric 
Company, at Harrison, N. J., died in Bermuda 
on January 1st, aged 50 years. 

He was a direct descendant of Jonathan 
Trumbull, the American Patriot, friend 
and adviser of Washington, and Colonial 
Governor of Connecticut. 

Marshall was graduated from the Scientific 
Course of Rutgers College in 1881, and went 
to work at the Edison Lamp Works, then at 
Menlo Park, in October of that year. 

In 1883 or 1884 he invented the comparison 
method of ph ring lamps, by which 

the voltage of a lamp a1 normal candle-power 
is determined without the use of electrical 
instruments. The lamp to be photometered 
is placed in multiple with a lamp of known 
candle-power and voltage and their relative 
candle-powers observed. A constant voltage 
line is nut required for this work, as the 
relative candle-powers of two lamps is the 
through a wide variation of voltage. 
Practically all carbon lamps manufactured 
by the Company are to this day measured 
for voltage by this method, which is very 
simple and enables an unskilled operator to 
ier of Ian 'lay. 

During the last few months Mr. Marshall 
completed and put in operation a very remark- 
able developmf nt ol the o >n method 
of lamp measuring, known as the watts-per- 
candle photometer. This photometer, as its 
name implies, gives the volts, amperes, and 



candle-power of a tungsten lamp at the 
desired watts per candle-power; the only 
electrical instrument required being a zero 
galvanometer. With this method, also, a 
constant voltage line is not necessary. Each 
photometer requires but one operator; his 
daily output, as well as the accuracy of his 
work, showing a marked increase over the older 
method, which entailed the use of a voltmeter, 
an ammeter, a constant voltage line, and a 
slide, rule calculation for each lamp. 

Beside- specializing in photometry, Mr. 
Marshall paid much attention to the manu- 
facture of carbon filaments, especially as 
regarded carbonization, and the practical 
methods of metalizing filaments at present 
in use are largely his. Mr. Marshall was 
a good mathematician and had a very lai 
capai or work, which he used to the 

limit . 

Personally, Mr. Marshall was universally 
loved and respected. A man of strong 
character and convictions, in him truthfulness 
and straightforwardness were so developed 
that he was incapable of the least degree of 
deception. He signed a total abstinence 
pledge when a boy, and never broke it. He 
lived a very simple life and found his recn 
tion and enjoyment in his garden, the woods 
and the fields. He knew the trees, plants and 
flowers growing in his neighborhood, and had 
many of them transplanted about his home. 
He was unmarried and devoted his life to his 
parents and sisters. 




VOL. XIII. NO. 3 »G«£ff%&l 9 % mt a V MARCH. I'M.) 

CONTFWTS 

Editorial ... . . . 99 

Some Chemistry of Light . . 1 1 1 1 

By W. R. Whitni s 

Commercial Electrical Testing, Part V . . 109 

By E. F. Collins 

The Johnsonville Hydro-Electric Development of the Schenectady Power Company . lis 

By John Liston 

Store Lighting 127 

By F. L. Heal* 

Starting Compensators 130 

By E. F. Gehrki ns 

A New Type of Meter for Measuring the Flow of Steam and Other Fluids . . 134 

B-s A. R. Dodge 

Transmission Line Calculations, Part VI ■ • 139 

By M. W. Franklin 

Regulation of the 1'rrcentagc of Carbon Dioxide in Furnace Gases . Ill 

By E. A. Basni s 

Pay-As-You-Enter Cars ... ... 143 

Obituary .' . . Ill 

Book Review .... • .111 




SOME CHEMISTRY OF LIGHT 
All electrical industries deal with a trans- 
mission and a transformation of energy. Con- 
sidering a typical case: mechanical energy 
from a steam engine or water wheel is trans- 
formed into electrical energy by the generator, 
transmitted some distance and re-transformed 
into mechanical energy by the motor. The 
transformations instead of being between 
electrical and mechanical energy may be 
between electrical and other forms; such as 
chemical energy, heat energy, or radiant 
energy. Of these transformations some are 
commercially of far greater importance than 
others. One of the first in importance is the 
conversion of electrical energy into radiant 
energy, or more specifically into radiant 
energy suitable for the production of light. 

All of these transformations involve losses, 
the lost energy usually appearing in the form 
of heat. Even in the case of a heating device, 
the efficiency is not perfect on account of the 
impossibility of applying or confining all of 
the heat at the desired point. Unfortunately, 
of all the energy radiated from a heated body 
only a small proportion, even under the best 
conditions, is of the proper frequency to 
affect our eyes and to be recognized as "light." 
In fact, there is no physical difference 
between radiant energy with a vibrational 
frequency too slow to give through our eyes the 
sensation of red, or too rapid to give the 
sensation of violet, and radiant energy which 
gives the sensation of light —the limitations 
of cokr arc physiological, that is, inherent 
in ourselves, and are not physically inherent 
in light producing bodies or in light itself. 
it follows, therefore, that since light is heat, 
it cannot lie produced without heat, and the 
best artificial illuminant that could ever be 
found would be that in which all the heat waves 
of the wrong frequency for lighl effects had 
been eliminated.. 

\n this number of the Revibw we print the 
recent presidential address of Dr. Whitney 
before the American Chemical Society, and 
while this paper was prepared for an audience 



of chemists, the outline of the research for 
artificial illuminants, gradually increasing in 
efficiency from crude oils and greases up to 
the modern incandescent tungsten and film- 
ing arc lamps, can be appreciated by others 
than those of chemical training. 

The present limitations in the number of 
candles per watt that can be obtained from 
incandescent lamps are in no way affected 
by the nature of the transformation from 
electrical to radiant energy, but solely by the 
ability of the filament to survive continued 
operation at high temperature without vapor- 
izing sufficiently to blacken the bulb or 
become disrupted. That the limitations lie 
in the nature of the materials and not in the 
process of light production is decidedly en- 
couraging. 

The modern tungsten lamp consumes, 
roughly, half as many watts per candle as 
the carbon incandescent lamp in its most 
highly developed form; this carbon lamp in 
turn consuming about half as many watts as 
the early incandescent lamps. Dr. Whitney's 
statement that the tungsten lamp can for a 
short time produce four or five times as many 
candles per wait as we now obtain from it in 
commercial service seems almosl equivalent to 
saying that discoveries will soon be made per- 
mitting lamps to operate commercially a1 better 
efficiency than has even yel Keen realized. 
Then' is no need to enlarge on the economic 
value of such improvements, and mention need 
only be made of the tremendous saving in coal 
that would at once lie effected by the reduction 

Of only a fraction of a wall per i andle. 

Incidentally, the paper may lead somi 
consider where the field of chemistry cud-: 
and physics begins. The dividing barrii r . 
which were never definitely drawn, seem dur- 
ing recent years to be lifol.cn down ai leveral 
and a lit tie reading between I he line 
of Dr. Whitney's paper shows thai the 
investigator inn i tudy hi.^ materials from 
the points of view of both the physicist and 
the chemist. 

John It Taylor 



100 



GENERAL ELECTRIC REVIEW 



THE FLOW METER 

At the present time much thought and 
energy are being expended in an effort to 
lessen the inroads that are being made upon 
our diminishing coal supply; on this account, 
the subject of the development and utiliza- 
tion of the water power available has assumed 
grave importance. For the same reason, 
anything that makes for economy in coal, 
whether it be by the substitution of water 
power or by the use of more economical 
steam boilers, more efficient engines, motors, 
lamps or what not, is of increasing importance 
precisely in proportion to the amount of coal 
it saves. 

In 1907 the stupendous total of over 474 
million tuns of coal, having a value of over 
$657,000,000, was mined in this country; to 
be used in the main for the generation of 
steam. Of this enormous annual output, a 
very considerable amount is absolutely wasted 
for lack of intelligent management in the 
generation, transmission and utilization of 
the steam; a lack that is due very largely, if 
not mainly, to the absence of simple and 
adequate means for measuring this product. 
I. the steam flow meters, described on 
another page of this issue, these means are 
provided, and for the first time the steam 
engineer is enabled to keep track of the 
generation, distribution and consumption of his 
steam in a thoroughly practical and effective 
manner, and consequently to manage his 
plant economically. 

The utility of the meters may be judged 
from the following list of some of the uses to 
which the recording type may be put: 

For recording the total amount of steam 
generated by a battery of boilers. 

For recording the amount of steam deliv- 
ered to any departmenl of a manufacturing 

plant. 

For recording the amount of steam sold 
for power, heating or manufacturing pur- 
pose 

For equalizing a load on individual boilers 
of a battery. 

For discovering losses originating from leaks 
between boilers and points of consumption 



which could not otherwise be detected; e.g., 
from defective traps, gaskets or valves. 

For discovering internal leaks in boilers as 
shown by the difference in the water input 
and the steam output. 

For determining the deterioration of effi- 
ciency of a boiler due to the formation of 
scale, etc. 

For determining the efficiency in the method 
of stoking, etc., etc. 

The value of these meters in determining 
distribution losses is indicated in the case of 
a certain underground main, of about 2000 
feet in length, which received 13,000 pounds 
of steam per hour and delivered but •'!( II II I 
pounds of this at the distribution points; 
10.000 of the 18,000 pounds being lost in 
transmission! 

This condition being discovered by the use 
of the meters, the main was unearthed, when 
it was seen that the covering had disinte- 
grated and some of the gaskets blown out. 
Repaired and re-covered, the main supplied 
four times its former load, with no increase 
in coal consumption. The saving in this case 
amounted to approximately $1S00 a month. 

Again, in some plants the steam used for 
heating is a large, though frequently uncon- 
sidered, item. In one manufacturing plant 
it was found by a meter that in November, 
this, together with the loss by radiation, 
amounted to over one-quarter of the total 
daily steam consumption, and thus on Sun- 
days, when no work was being performed, 
the boilers were still carrying one-quarter of 
the regular weekday load. 

The chart of the recording meter, showing 
as it does the steam consumption from hour 
to hour, is, in effect, a work record, and like 
the peak load chart of a central station, 
shows the hours of greatest manufactur- 
ing output. It has been noted that in 
the morning the rate at which work is 
being done gradually increases until about 
eleven o'clock, after which it declines until 
noon; though through the morning the rate 
of production is pretty well maintained. 
Again, immediately after the midday rest 
and meal, the rate of work goes up, but 
gradually sags as the afternoon advances 
until toward the end of the day the falling 
off is rapid. 






101 



SOME CHEMISTRY OF LIGHT* 

By W. R. Whitney, Ph. D. 

Director of Research Laboratory of Schenectady Works 



From the dawn of history, chemistry has 
had much to do with the production of 
artificial light, and I wish now to recall to 
your minds a few illustrations. I will not 
burden you with a long story on physics or 
mechanics of light, but* intend treating 
the subject of artificial light so as to show 
you that it has always been largely a subject 
for chemical inYcstigation. I want to impress 
upon your minds that it is still a most green 
and fertile field for the chemist. It should 
be borne in mind that I am trying to interest 
an audience of chemists from widely dif- 
ferent fields, rather than to present a chron- 
ological record of recent experimental re- 
search. 

I can not tell just when chemistry was 
first scientifically applied to a study of 
artificial light. Most cardinal discoveries 
are made by accident and observation. The 
first artificial light was not made by design, 
nor was the first improvement the result of 
chemical analysis. It is supposed that the 
first lamps were made from the skulls of 
animals, in which oil was burned. Herod- 
otus, describing events about three centu- 
ries before Christ, says of the Egyptians: 

"At the times when they gather together at 
the city of Sais for their sacrifices, on a certain 
night they all kindle lamps many in number 
in the open air round about the houses: 
now the lamps are saucers full of salt and oil 
mixed and the wick floats of itself on the 
surface and this burns during the whole night." 

This night was observed all over Egypt 
by the general lighting of lamps, and these 
lamps were probably the forerunners of the 
well-known Greek and Roman lamps of 
clay and of metal which arc so common in 
our museums. 

The candle and lamp were probably in- 
vented very much earlier. We know that 
both lamps and candles were u ed bj the 
priests of the Jewish temple as early as 
900 B.C. The light of those candles and 
lamps was due, as you know, to particles 
of carbon heated in a burning gas. 

It is not fair to the chemists of our early 
candle-light to skip the fad that greal 
chemical advances were made vhile candle 

* Presidential address delivered before the American Chem- 
ical Society. December 29. 1°0°. 



were the source of light, and so I touch for 
a moment upon one of the early applica- 
tions of chemical knowledge. The fats and 
waxes first used were greasy and the lighl 
was smoky and dull. They were capable 
of improvement and so the following chem- 
ical processes were developed and applied 
to the fats. They were firsl treated with 
lime, to separate the glycerol and produce 
a calcium soap. This was then treated 
with sulphuric acid, and the free stearic 
and palmitic acids separated. These acids 
were then made into candles and gave a 
much whiter light than those containing 
the glycerol ester previously used. Similar 
applications of chemical principles are prob- 
ably known to you all in the refining of 
petroleum. The crude distillate from the 
rock oil is agitated with sulphuric acid 
and then washed with a solution of sodium 
hydroxide. This fact accounts, in consid- 
erable degree, for the advance of a number 
of other chemical processes. An oil re- 
finery usually required the presence of a 
sulphuric acid plant in the immediate vicinity, 
and this often became a source of supply 
for other new chemical industries. 

V ry great advances have been made in 
the use of fats and oils for lighting pur- 
poses, but there is so much of greater in- 
terest in later discoveries that we will not 
consider many of them. The distillation 
of gas from coal or wood in 17:1!) was a 
chemical triumph, and a visit to a gas plant 
still forms one of the main attractions to 
the young chemist in an elementary course 
of applied chemistry. The first municipal 
gas pl.mi was established in London, just 
aboul one hundred years ago. The ge 
plan, :o apparently simple to us to-day, was 
at its inception iidged impracticable by 
engineers. 

In spite of other method i of illuminal ion, 
the improvements in the making, purification 
and application of illuminatio have 

caused a tea rea ' ' owes 

its illuminating power to tb 
of the carbon in it is heated to incandescence 
during the combu ion of the gas. It must 
contain, therefore, such carbon compounds 
ag yjgifj ; , f a ii . o carbon, and this 

knowledge ha i led to the >< heme:, for the 



102 



GENERAL ELECTRIC REVIEW 



enrichment of gas and for the use of non- 
luminous water-gas as a base for illuminating 
gas. 

Various schemes were devised in the 
early part of the nineteenth century for 
using gas to heat to incandescence, rods or 
surfaces of lime, zirconia and platinum. 
This was not at first very successful, owing 
to imperfect combustion of the gas. The 
discovery of the Bunsen-burner principle 
was made a little later. By thus giving a 
much higher temperature to the gas flame 
and insuring complete combustion, new 
impetus was given to this branch, and the 
development of suitably supported oxide 
mantles continued for half a century. 

Most prominent in this field is the work 
of Auer von Welsbach. It was a wonder- 
ful series of experiments which put the 
group of rare earth oxides into practical 
use and started a line of investigation which 
is still going on. The Welsbach mantle 
practically substitutes for the carbon of 
the simple gas flame, another solid in a finely 
divided shape capable of giving more efficient 
light. This allows all of the carbon of the gas 
to contribute to the production of a hotter 
flame. But more interesting than the 
mechanical success, to my mind, is the unfore- 
seen or scientifically unexpected discovery 
of the effect of chemical composition. By 
experiment it was discovered that the inten- 
sity and color at incandescence of the various 
mixtures of difficultly fusible oxides varied 
over a wide range. Thus a broad field for 
unforeseen investigation was opened, and 
much advanced chemical work has been 
applied to this industry. The color and 
intensity of the light varies in an unexplained 
manner with slight differences in composition 
of the mantle. The following are the compo- 
sition and candle-powers of some sample 
mantles: 

CANDLE-POWER OF MANTLES, RANGING 

FROM PURE THORIA TO 10 PER 

CENT. CERIA 

tii Per Cent Candle- 

No. Thoria Ceria Power 

367 100.00 0.00 7 

378 !''.i 7.". 56 

369 99 50 77 

371 99 0.75 85 

:;71 99.00 l 00 88 

•i7L' 98.50 1.50 79 

98 2.00 :r. 

374 '.17.1111 65 

:;7."» 95.00 44 

370 90 10.00 Jo 

60 La.Zr, Ce Oxides 30 



The methods of making the present mantles 
were also a part of Dr. Auer's contribution 
to the art. Suitably woven fabrics are 
dipped into solutions of the rare earth 
salts; these are dried and the organic mat- 
ter burned out, leaving a structure of the 
metal oxides. 

The pure thoria gives a relatively poor 
light. The addition of the ceria, up to a 
certain amount, increases the light. This 
added component is called the "excitant," 
and as the cause for this beneficial action 
of the excitant is not known, it is possible 
that further discoveries along this line will 
yet be made. 

There is hardly a prettier field for chemical 
speculation than is disclosed by the data on 
these light efficiencies. For some unknown 
reason, the change in composition by as little 
as one per cent, varies the luminosity over 
ten-fold, and yet more than one per cent, of 
the excitant (ceria) reduces the light. Be- 
sides the temptation to speculation, such 
disclosures of nature encourage us to put 
greater trust in the value of new experi- 
ments, even when accumulated knowledge 
does not yield a blazed trail for the pioneer. 
By giving a discovery a name and attach- 
ing to it a mind-quieting theory, we are 
apt to close avenues of advance. Calling 
this small amount of ceria an "excitant" 
and guessing how it operates, is directly 
harmful unless our guess suggests trial of 
other substances. 

One of the explanations proposed to 
cover the action of the ceria ought to be 
mentioned, because it involves catalysis. 
This is a term without which no chemical 
lecture is complete. Some think that the 
special mantle mixture causes a more rapid 
and localized combustion and therefore higher 
temperature, by condensation of gas in 
its material. Others think that this par- 
ticular mixture permits of especially easy 
and rapid oxidation and reduction of its 
metal oxides themselves in the burning gas 
mixture. The power which catalyzers have 
of existing in two or more states of oxida- 
tion seems to apply also to the ceria of the 
Welsbach mantle. 

Whatever the truth may be, it has been 
shown by Swinton * that when similar o- 
mantles are heated to incandescence in vacuo 
by cathode rays, the presence of one per cent, 
ceria produces only a very small increase in 
the luminosity of thoria. It is interesting 

•Proc. Roy. Soc.. 66. 115. 



SOME CHEMISTRY OF LIGHT 



in:; 



to note that in the gas flame pure ceria gives 
about the same light as pure thoria, while 

in the cathode rays of the Crookes tube. with 
conditions under which ceria gave almost no 
light, pure thoria gave an intense white 
light. These facts, which are still unex- 
plained, illustrate how little is understood 
in this field. 

I will merely refer to the fact that vapors 
of gasoline, kerosene, alcohol, etc., arc now 
also used in conjunction with the Welsbach 
mantles. The field of acetylene I must also 
omit with a mere reference to the fact that 
the manufacture of calcium carbide was a 
chemical discovery; and the action of water 
upon it, producing the brilliantly-burning 
acetylene gas was another. 

Turning now to electrical methods of 
generating light, we find the chemist early 
at work. Sir Humphrey Davy and others, 
at the dawn of the nineteenth century, 
showed the possibilities which since that 
time have been developed into our various 
types of incandescent and arc lamps. We 
naturally attach Mr. Edison's name to the 
development of the carbon incandescent 
lamp, because it was through his inde- 
fatigable efforts that a practicable lamp 
and illuminating system were both devel- 
oped. 



It had long been known that platinum, 
heated by the current, gave a fair light, 
but it melted too easily. A truly enormous 
amount of work was done in attempts 
to raise the melting-point of the platinum, 
and the effect of occluded gases, of annealing, 
of crystalline condition, etc., were most 
carefully studied, but the results \\ 
unsatisfactory. He was therefore led to the 
element carbon as the next most promising 
conductor of high melting-point. Edison's 
persistent and finally successful attempts to 
get a dense, strong, practical filament of 
pure carbon for his lamps, is one of the 
most encouraging lessons to the chemist of 
to-day. 

This history needs to be read in the light 
of the knowledge of carbon at that time and 
the severe requirements of a commercially 
useful carbon filament. It illustrates the 
value of continued effort when it is based on 
knowledge or sound reasoning. The search 
was not the groping in the dark that some of 
us have imagined, but was a resourceful 
search for the most satisfactory, among a 
multitude of possible materials. From out- 
point of view, all subsequent changes in 
choice of material for incandescent lamp 
filaments have been dictated by the knowl- 
edge that high melting-point and low vapor 



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104 



GENERAL ELECTRIC REVIEW 



tension were the first requirements. If you 
will consult the curve (Fig. 1) of the melting- 
points of all the elements, as plotted against 
their atomic weights, you will see at once that 
the desired property of high melting-point 
is a periodic function of the atomic weight. 
And it is this fact, which was independently 
disclosed as a general law by Meyer and 
Mendeljeff, in 1869, that has aided in the 
selection of all the new materials for this 
use. You will notice that the peaks of 
the curves are occupied by such elements 
as carbon, tantalum, tungsten, osmium, 
etc., which are all lamp materials. 

A study of the laws of radiation also 
soon played a part in incandescent lamp 
work. The early rough and black filament 
of bamboo was first replaced by a polished 
black carbon filament, and later by one 
which had a bright, silver-gray coat of 
graphite. A black body at any tempera- 
ture radiates the maximum possible energy 
in all wave-lengths. Heated to incandes- 
cence, it will radiate more invisible and 
useless infra-red rays than any other opaque 
material at the same temperature; a polished 
metal is therefore a more efficient light 
source than the same metal with a black. 
or even rough surface. This fact is derived 
from Kirchoff's law of radiation and absorp- 
tion, w hich was early established. 

It may seem like penetrating too far into 
details to consider for a moment the changes 
in structure and surface' which the carbon 
filament of our incandescent lamps has 
undergone, but the development of such 
an apparently closed problem is instructive, 
because it has yielded to such simple methods 
of attack. The core, or body, of the carbon 
filament of to-day is made by some one 
of the processes based on dissolving and 
reprecipitating cellulose, such as are used 
in artificial silk manufacture. The cellulose 
solution is squirted through a die into a 
liquid which hardens it into dense fibers. 
These cellulose fibers arc then carbonized by 
being heated, out of contact with the air, at 
as high a temperature as possible with gas 
furnaces. All of this is also merely the 
application of chemistry which was first 
worked out in some of the German cherni 
laboratories. 

This plain carbon filament (the result of 
this simple process), which might have been 
satisfactory in the early days, would nowa- 
days he useless in a lamp, as its practical life 
is only about 100 hours at .'! watts per candle. 



In a subsequent process of manufacture it 
is therefore covered with a steel gray coat- 
ing of graphite, which greatly improves the 
light emitting power. This coat is pro- 
duced by heating the filament in an atmos- 
phere of benzene or similar hydrocarbons. 
The electric current which heats the fila- 
ment is of such an intensity that the decom- 
position of the hydrocarbon produces a 
smooth, dense deposit of graphite. 

With this graphite-coat the filament now 
burns about 500 hours. But the simple 
graphite coat is improved by being subjected, 
for a few moments, to a temperature of 
about 3,500° in the electric furnace; the life 
then becomes about 1,500 hours under the 
same operating conditions as before. The 
product of this treatment is known as the 
metallized filament, because by this last step 
its temperature coefficient of resistance is 
made similar to that of the metals; i.e., 0.0037. 

With an incandescent lamp containing a 
platinum wire filament, the intensity of 
its light is not very great, even when the 
current is sufficient to melt the wire. A 
much greater luminosity is produced by a 
plain carbon filament, and a still greater 
by the graphite-coated and metallized car- 
bon before they are destroyed. In the case 
of carbon, the useful life of the lamp de- 
pends much more on the vaporization of 
the material than on its melting-point, and 
these lamps will operate for a short time 
at very much greater efficiencies or higher 
temperatures than is possible when a prac- 
tical length of life is considered. Thus, 
besides the physical effect of surface quality, 
we have evidence of differences in the vapor 
pressure of different kinds of carbon. It 
looks as though carbonized organic matter 
yielded a carbon of much greater vapor 
pressure for given temperature than graphite, 
and that even graphite and metallized 
graphite are of quite distinctly different 
vapor pressures at high temperatures. It 
may be interesting to note here that if the 
carbon filament could withstand for 500 
hours the maximum temperature which it 
withstands for a few moments, the cost of 
operating incandescent lamps could be re- 
duced to nearly a fifth of the present cost. 

It was discovered by Auer von Welsbacb 

that the metal osmium could be made into 
a filament, though it could not be drawn as 
a wire. The osmium lamp was the first of 
the recent trio of metallic filament incan- 
descent lamps. The tantalum lamp, in 



SOME CHEMISTRY OF LIGHT 



in:, 



which another high melting-point metal 
replaces the superior but more expensive 
osmium, has been in use six or eight years. 
This surpasses the carbon in its action, and 
on running up to its melting-point it shows 
still brighter light than carbon. 

More recently the tungsten filament lamp 
has started to displace both of the others. 
At present this is the element which with- 
stands the highest temperature without 
melting or vaporizing, and on being forced to 
its highest efficiency in a lamp it reaches 
higher luminosity; it is similar to carbon and 
tantalum in that an enormously greater 
efficiency may be produced for a very short 
time than can be utilized for a suitable length 
of life. The inherent changes at these tempera- 
tures, distillation or whatever they are, 
quickly destroy the lamp. The lamp will 
burn an appreciable time at an efficiency 
fifteen times as great as that of the common 
operating carbon incandescent lamp (at 3 
watts per candle). In other words, light 
may be produced for a short time at an 
energy-cost one fifteenth of common prac- 
tice, so that there is still a great field for 
further investigation directed towards merely 
making stationary those changing conditions 
which exist in the burning lamp. 

While it is generally true that the light 
given by a heated body increases very rap- 
idly with rise of temperature above 600°, 
the regularity of the phenomenon is com- 
monly over-estimated. A certain simple 
law covering the relation between the tem- 
perature and the light emitted, has been 
found to apply to what we call a 
black body. This so-called Stefan- Boltz- 
mann law states that "the total intensity 
of emission of a black body is proportional 
to the fourth power of the absolute tem- 
perature." There are, however, very few 
really black bodies in the sense of the law. 
The total emission from a hole in the wall 
of a heated sphere- has been shown experi- 
mentally to follow the law rigidly, hut must 
actual forms and sources of illumination 
do not. Most practical sources of artificial 
light are more efficienl light producer; than 
the simple law requires. This may be said 
to be due to the fact that these substances 
have characteristic powers of emitting rela- 
tively more useful energy as light than 
energy of longer wave-length (or heal rays). 
Most substances show a powei of selective 
emission and we might say that an untried 
substance, heated to a temperature where it 



should be luminous, could exhibit almost 
any conceivable light effect. A simple 
illustration will serve to make this clear: 
[f a piece of glass be heated to 600°, it does not 
emit light; if some powder such as clay be 
Sprinkled upon it, light is emitted, and the 
proportion of light at the same temperature 
will depend upon the composition of the 
powder. Coblentz has shown, both for the 
Auer mantle and for the Xcrnst glower, 
that the emission spectra are really series 
emission bands in that portion of the energy 
curve which represents the larger part of the 
emitted energy. This is in the invisible 
infra-red pari, and so the laws which govern 
the emission at a given temperature depend 
upon the chemical composition of the radiant 
source. Silicates, oxides, etc., show character- 
istic emission bands. 

One of the most attractive fields of arti- 
ficial light production has long been that of 
luminous gases or vapors. It has seemed 
as though this ought to be a most satisfac 
tory method. The so-called Geissler tubes 
in which light is produced by the electrical 
discharge through gases at low pressure are 
familiar to all. The distribution of the 
energy emitted from ga^es is still further 
removed than that of solids from the laws 
of a black body, and a large proportion of 
the total electrical energy supplied to a 
rarefied gas may be emitted as lines and 
bands which are within the range of the 
visible spectrum. These lines, under defi- 
nite conditions of pressure, etc., arc charac- 
teristic of the different elements and c im- 
pounds. The best known attempts to util- 
ize this principle are the Moore system of 
lighting (in which Ion- tubes of luminous 
gas are employed), and the mercury Lamps, 
which, while more flexible on account of 
size, are still objectionable because of i ln- 
color of the light. 

It is rather interesting that the efficien 
ie of all of these varii iu < >un i 
trie Light are not nearly so widely different 

as one would expeel from a con idera ii ill 
of the widely divergent methods of light 
product ion employed. 

Prom t he light of a vapor oi gas to 
of an open are is not a wide itep, hut the 
con in ion in the an- are apparently quite 
complex and there is a great deal of room 
for interesting speculation in the phenom- 
ena of an arc. Briefly, the hinds 
of arcs to be --ii idered in lighting. One 
has been in use for a century, the othe 



106 



(VEXERAL ELECTRIC REVIEW 



a few years only. The first is the successor 
to Sir Humphrey Davy's historical arc 
between charcoal points. In this kind of 




















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Wave Leri$t/> 

Fie. 2 






arc the current path itself is hardly lumi- 
nous, and the light of the lamp is thai 
by the heated electrodes. In case of d 
current it is the anode, or positive elec- 
trode, which and gives far 
the greater part of the light. In this car- 
bon arc, it can readily be seen that the light 
is cmiiicd by the heated solid carbon i 
electrode; this givi dy source of light, 
Imt is not so efficienl as an arc in which ma- 
in the arc stream itself is the source of 
light. The are may be made to play upon 
rare earth oxides, and these, being heated to 
incand . increase the luminosity, but 
this 1 d useful. The more 

way is to introduce into the carbon 

electrode certain salts whicl ■ into the 

arc and give a luminou Here cerium 

fluoride, calcium fluoride, etc., are used, and 

olor of i he arc, jusl as in the ca 



gas mantles, may be varied by varying the 
composition of the electrodes. This is seen 
in the arc from the carbon electrodes con- 
taining such salts. 

In the case of the flaming arc, the greater 
part of the light is due to the incandi 
metallic vapors in the space between the 
electrodes. Substitution of one chemical 
for another in such flaming arc electrodes 
has covered quite a wide range of chemical 
investigation. Salts are chosen which give 
the greatest luminosity without causing the 
formation of too much ash or slag. Some 
compounds of calcium, for example, are 
practicable, while others are not, though all 
of these would, under suitable conditions, 
yield the calcium spectrum. If such salts as 























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Wave Le/igtf? 

Fig. 3 

ii fluoride were conductors at ordinary 
temperature, useful electrodes for flame 
arcs would probably be made from them. 
Such conducting materials as iron oxide, 
carbid have been used for flame ard 

. and a great many of the so-called 
magnetite arcs arc now in use. The electrodes 



SOME CHEMISTRY OF LIGHT 



107 



in this case are largely magnetic oxide of iron, 

with such other ingredients as titanium and 
chromium oxides, to increase the intensity 
of light, to raise the melting-point of the 
mixture, etc. 


























P/at/f>um 
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r £ 3 4 5 6 ? 

Fig. 4 

As will In' seen from observing this are, 
the light is very white and in en • and is 
generated 1>\ tin- heated vapors of thi 
proper. A great many modifications of 
this arc principle arc possible. Titanium 
carbide and similar substances give charac- 
teristic arcs, and some of them arc very 
intense and efficienl . 

The Nernst Lamp 

A distinct species of electric incande cenl 
lamp is that invented about ten 
by the well-known physical ehemist, Pro 
fe or Nernst. This employs tor filaments 
a class of bodies which are not electrical 
conductors at all at ordinary temperatures, 



and which, at their burning temperatures, 
do ii,,t conducl the currenl as metals and 
carbon, but as a solution does. This kind 
of conductivity, the electrolytic, involves 

electrochemical decomposition at thi 
trodes, and in the ease of the Nernst 61a 
ments these otherwise destructive reactions 
are rendered harmless by the continual 
oxidizing action of the air. For this rea o 
this type of lamp will not burn in vacuo. 
For its most perfect utility the principle of 
the Nernst lamp seems to require a mixture 
of oxides, because a single one is not so 

g 1 a conductor nor so luminous. It uses 

oxides because these are the most stable 
compounds known, and it uses the rare 
earth oxides because they have higher mell 
ing-point than other oxides. As the effi- 
ciency rises very rapidly with temperature, 
there is a great advantage in using the most 
infusible base possible. For that reason, 
zirconia, thoria, etc., are usually employed. 

In this lamp a rod or filament of an oxide 
mixture, much like those used in Wclsbach 
mantles, is heated by the currenl, externally 
applied, until it reaches a temperature at 
which it becomes a good conductor itself. 
Here again the peculiar laws of light radia- 
tion are illustrated, the light emitted at a 
given temperature being determined by the 
nature of the substance. Just as the pure 
thoria gives a poor light compared to the 
mixture with one per cent, eeria, so a pure 
zirconia rod, heated by the current, gives 
much less light than a rod containing a 
little thoria, eeria or similar oxide. Work 
done by Coblentz on the energy-emission of 
such rods shows the emission spectra, at 
in the infra-red, to vary with the 
nature of the substance. In general, thi 
ia arc not continuous like I lie spectra 
of metals and black- ho. lies, bu1 seem to 
ici up) ;m intermediate po ;i1 ion bet 
these and luminous gases, which we know 
have usually distincl line spectra. 

This recalls the subject of selective emis- 
sion. Coblentz has shown elective emis- 
sion in thi lengths for a Nernst 
r. This is shown in co irison with 
.i blai 1. body, in curve 

No. 2. Tl . when compared 

at the tempera here they exhibit the 

same wave-length for maximum cmi 
differ very con iderabl; it ■ "i in the 

infra-red, the black bod 
ergy a1 the blue end, and less at tb 



108 



GENERAL ELECTRIC REVIEW 



This is still more noticeable in the curves 
for such substances as porcelain, magnesia 
and glass, as shown by Coblentz's curves 
(Fig. 3). 

The curves of wave-length and radiant 
energy which are shown are, with slight 
modifications, taken from work of Lummer 
and Pringshein and of Dr. Coblentz. The 
curve for the ideal, or black body radiator, 
gives a picture of the total energy and 
its distribution over the different wave- 
lengths. It is the peculiarity of the black 
bod to radiate more energy of any given 
wave-length than does any other body at 
the same temperature. Therefore, in case 
of all substances acting as thermal radi- 



mum energy or wave-length corresponding 
to maximum energy, shifts gradually to- 
wards the left, or towards the visible wave- 
lengths. 

It is this rapid shifting of the position 
of maximum energy which makes the search 
for substances which can withstand even 
only slightly higher temperatures of such 
great interest. 

The curves for the black body and for 
platinum (dotted lines) are not greatly 
different in general appearance, but the 
total amount of energy emitted at a given 
temperature from the black body is shown 
to be more than for the platinum, and it 
can be seen that at about the same teni- 




ae 0.4 



0.8 LO 



Wave Length 

Fig. 5 



2.0 



3.0 



ators, the black body will always give the 
greatest brilliancy. Since this body at the 
time radiates a maximum in all wave- 
lengths, it will be surpassed in light effi- 
ciency by any substance which is a rela- 
tively poor radiator in the invisible or non- 
luminous part of the spectrum. 

In the energy curves shown it is to be 
noticed thai thi visible part of the energy 
is practically only thai between 0.4 and 0.8 
thousandths of a millimeter. Consider the 
solid lines in Fig. I for a moment. These 
show the emission of a black body at centi- 
grade temperatures noted on the curves. 
Evidently the energy emitted rises very 
rapidly with the ture; i.e.. as the 

fourth power of the absolute temperature. 
It will be noted also that the point of maxi- 



perature the platinum is the more econom- 
ical light source. Professor Lummer has 
said thai at red heat, bright platinum does 
not radiate one tenth the total energy which 
the ideal black body radiates at the same 
temperature, and al the highest temperature 
still less than one half. The deviation 
of platinum from the black body law is 
a step in the direction of getting improved 
light-efficiency without corresponding in- 
of temperature. This method is 
practically without limit in its extension, 
for there seems to be no limit to the forms 
of energy curves which different substances 
may possess. The curves are apparently 
determined not only by physical state, 
but also by chemical composition of the 
emitting substance. 



COMMERCIAL ELECTRICAL TESTING 



10!) 



In the production of artificial light, the 
tendency will always be in the direction 
of increasing the practical efficiency; i.e. 

reducing the cost of light. We have seen 
that there is still much rnom for this. In 
the case of the kerosene oil lamp we know 
that much less than one per cent, of the 
energy of combustion of the oil is radiated 
as light from the flame. In the case of the 
most efficient source — the electric incandes- 
cent lamp at highest efficiency— we are still 
far from ideal efficiency. A still higher 
temperature would yield a yet higher effi- 
ciency. We do not know exactly how much 
light might possibly be yielded for a given 
consumption of energy, but one experi- 
menter concludes that it is about ten candles 
per watt. Fortunately, it is not now clear just 
how the chemist is to realize all the ad- 
vances which he will make in more efficient 
lights. 

No consideration of this part of the sub- 
ject is complete without a brief reference 
to the efficiency of the firefly. The source 
of his illumination is evidently chemical. 
This much is known about the process: 

The light-giving reaction is made to 
cease by the removal of the air, and to in- 
crease in intensity by presence of pure 
oxygen. It is extinguished in irrespirable 
gases, but persists in air some time after 
the death of the insect. Its production is 
accompanied by the formation of carbon 
dioxide. These ail indicate a chemical 
combustion process. Professor Langley has 
shown that such a flame as the candle 
produces several hundred limes as much 
useless heat as the total radiation of tin 
firefly for equal luminosity. In other 
words, the firefly is the mosl efficient light 
source known. This is illustrated by I 
energy distribution curves from several light 
sources taken from Professor Langley's work 
(Fig. 5). The difficulties attendant upon the 
accurate determination of the curve for the 
firefly an o r. at that we ought not 
expect very great accuracy in this ca ;e. 
These curves, which in each ease refer to the 
energy after passing through glass, which 
cuts off energy of long wave Lengths, repre i 
the same quantities of radiant energy. 
While the sun is much more efficienl Mian the 
gas flame or carbon are, it still ; far 

the large I part of it en rg m the invi ible 
long wave-lengths (aboi e 0.8), while the firefly 

eet havi its radiant energy confined to 

a narrow part of the visible spectrum. 



COMMERCIAL ELECTRICAL 
TESTING 

Part \" 

By E. F. Collins 
Tec hnical Superintendent 
General Electric Company 

Commutating Poles 

The commutating pole produces the nec- 
essary flux for neutralizing the effect of 
armature reaction, and prevents that shifting 
of the electrical neutral point between no 
load and full load which occurs in direct 
current machines not equipped with com- 
mutating poles; and, in addition, aids the 
current reversals in the armature coils at 
commutation. To obtain the reversal with- 
out sparking, with normal load current 
flowing, a definite number of ampere turns 
is required. In many cases, fractional 
turns are necessary in the commutating 
field winding; but as only whole turns 
or half turns are possible for mechanical 
reasons, a shunt is connected across the 
terminals of the commutating field winding 
and adjusted in test to shunt the current in 
excess of that required. As the electrical 
neutral does not shift, the brushes are set on 
the no-load electrical neutral, the adjustments 
made, and the rocker arm chisel-marked for 
thai setting. Because of this position of the 
brushes, the machine is sensitive to conditions 
thai under-excite the commutating poles, 
or make them inactive. Such conditions may 
"i e 'lie neutral to shift, resulting in bad 
sparking at the brushes or even a 3a ;h over, 

particularly in the Ci f machines of 500 

volts or over. 

Consider, for instance, a 300 kw., 500 volt 
generator, with a heavy german silver shunt 
across the terminals of the commutating field 
winding. If the machine is short circuited, 
the inductance of i he commutal tng field coils 
the instantaneous heavy overload 
currenl through the non-indu i ermarj 
silver shunt and leave the commutating 
field without sufficienl i meu ralize 

armature reaction. The ! neutral 

diately shifts and had commutation 
3. To eliminate this trouble, an 
inductive shunt is used aero ninals 

of the commutatin and must 

always be in circuit whi i ichine in 

i under load. If dl occurs, the 

inductani shunt, bein than 



110 



CEXERAL ELECTRIC REVIEW 



that of the commutating field winding, 
the heavy line current through the 
field winding and tends to keep the com- 
pensation normal for all conditions of load. 

Inductive Shunt 

An inductive shunt i> used on all machines 
ol 500 volts or more, of a normal current 
-i 100 amperes or gr< ater. As a to 

ary to determine exactly how much 
current must be shunted from the corn- 
mutating field, the inductive shunt is designed 
with an inductance rea er than that of the 
commutating field winding and with low 

nice and ample current carrying capac- 
ity. Any additional resistance necessary is 
obtained by connecting german silver in 

with the inductive shunt, the length and 
resistance of which is varied till an adjustment 
is obtained that gives practically perfect 
commutation throughout the whole load 
range for which the machine was designed. 

Location of Electrical Neutral 

After a commutating pole machine has been 
brought to normal voltage at no-load, the 
no-load electrical neutral must lie located. 
To do this, a fibre brush of the same size as 
the carbon brushes on the generator in test 
must be procured. This brush should have 
boles drilled through it, each of which 
will take a No. 11' bare wire: the spacing be- 
tween the holes being equal to the distance 
between adjacenl commutator bars. The 
wires should lie small enough to move freely 
through the holes, otherwise they may stick 
ami make poor contact on the commutator, 
or become wedged and bear on the com- 
mutator so hard as to score it badly. One 
carbon brush should be removed from its 
holder and the fibre brush inserted in its 
place, with the two wires in the brush eon 
nected to a low reading, or millivoltmeter. 
With normal volts no-load on the generator, 
the brushes should be shifted till the in 
ment needle has passed through the zero 

, and then back again until the instru- 
ment again indie i, to make sun- that 

tual zero has been found. Pencil mark 
the rocker arm for this shift and then move 
the tibre brush to each of the other studs 

sively, shifting the brushes, if necessary, 
till zero reading is obtained, and pencil-mark 
the rocker arm for each stud. If a different 
shifl is required to locate the neutral of the 
different studs, shift the brushes to a position 
which is the mean of all the different positions. 



With the brushes set in the mean position and 
the inductive shunt properly connected, put 
on normal load and note the commutation. 
If commutation is not practically sparkless at 
normal load and rated overload, take off 
the load and field excitation, and connect 
a german silver shunt across the commutatins. 
field terminals. If the machine requin 
inductive shunt, the german silver and 
inductive shunts are connected in series. 
With the total shunt resistance great enough 
to shunt not more than 10 per cent, of normal 
load current, full load is applied and commu- 
tation noted. The length of the german silver 
is changed and the commutation is tested 
until an adjustment has been obtained which 
gives the best commutation throughout the 
range of load required. An ammeter is then 
eon nected in and the number of amperes 
flowing through the shunt circuit read and 
recorded. In case satisfactory commutation 
cannot be secured, the wiring, spool assembly, 
pole and brush spacing, air gap, polarity. 
spacing of equalizing rings, etc., should be 
checked. If these are all found to be correct, 
the fibre brush should be used again and the 
full load neutral of each stud tested. If an 
appreciable voltage is obtained bet 
adjacent bars, the brushes should be care- 
fully shifted until zero voltage is obtained, 
and the shunt across the commutating field 
readjusted. With the best shunt adjustment 
possible, the fibre brush should be used on 
each stud, and readings made of the current 
shunted and the shift of the brushes from the 
no-load neutral. 

If the full-load electrical neutral of one or 
more studs is found to differ appreciably from 
that of the others, the commutating pole 
spacing, brush spacing, and air gaps of those 
poles and studs which affect the neutral in 
question should be carefully checked. 

When a final adjustment has been obtained 
on any commutating pole machine of 200 kw. 
or greater, the fibre brush should be used on 
each stud and the results with full load 
recorded. 

In general, shunting current from the 
commutating field will shift the load neutral 
of all studs away from the no-load neutral by 
the same distance. Shunting less currenl 
will shift all neutrals toward the no-lodd 
neutral. Where possible, all adjustments 
should be mack- with the brushes on the no- 
load neutral, and the brushes should be left 
permanently in that position. The rocker arm 
of all commutating pole machines should be 



COMMERCIAL ELECTRICAL TESTING 



111 



plainly chisel marked, when the final adjust- 
ment has been made. When satisfactory 
commutation has been obtained, a heavy load 
should be thrown on and off suddenly and a 
record made of tin- resultant commutation 
and general behavior of the machine. If the 
machine has an inductive shunt , and Sashing 
or violent sparking is produced by throwing 
a heavy load on and off quickly, readjusting 
the air gap of the inductive shunl should lie 
tried. 

"With a given winding on the core, the 
inductance of the shunt may be varied by 
changing the gap, and the relative inductance 
.if the shunt and commutating field winding 
be thus adjusted. If the current in the shunl 
circuit quickly falls to zero when a heavy L iad 
is thrown off by tripping the breaker, and the 
brushes show sparking, there is too little 
inductance in the inductive shunt and its air 
gap should be decreased. The air gap should 
be adjusted to give the minimum sparking 
when the machine is operating with a highly 
fluctuating load. 

Baking Commutator 

To bake the commutator on a commutating 
pole machine, the brushes should never be 
shifted under load to produce sparking anil 
heating. They sin mid always lie shifted at 
no-load to insure against setting them 1« 
the safe limit of no-load commutation, thus 
preventing flash-over should the load be 
suddenly removed. When baking a com 
mutator, it should also be remembered that 
the armature must not be short circuited 
through the commutating pole winding, as in 
this case the majority of machines will build 
up as series generators and the armature 
current cannot then be controlled. 

DIRECT CURRENT MOTORS 

The connections and wiring of all mi 
should be carefully examined, with parti 
reference to the field. At starting, the 
of the machine must lie carefully followed 
with a tachometer, and the circuit bn 
immediately opened if the ipeed rises above 
i ire icribed limit. 

With the starting rheostat or water box in 
th< off position, the terminal of the rhi 
or box must be attached across the open main 
switch, with the circuit breaker i ' 
the lower terminal being attached first. 
The field switch should then 1" closed and 

the pole pieces tested with a piece oi 

for excitation. The resistanc 



main .witch should then be gradually cut oul 
and, if the speed is all right, the main switch 
cli >sed. 

If the motor runs above normal speed the 
wiring should be carefully examined I 
that the field is connected across the circuit. 
Sometimes by mistake the field is connected 
across the main switch: in which case a 
as the Starting resistance is cut out the field 
current falls rapidly and the motor speeds 
up excessively. To test for wrong conni 
read volts held during starting and, if the field 
is wrongly connected, the volts field will drop 
as the starting rheostat is cut out. 

If a potential curve cannot he taken on a 
motor with a multiple wound armature by 
running i1 as a generator, a "motor potential 
curve" maj be taken by the following 
method: The machine is run as a motor with 
the field self-excited, the field current is held 
con tant, and a constant voltage is applied 
to the armature, using only two adjaci nl 

■ .I bru In; on the commutator. A care- 
ful reading of the speed is then taken. The 
brushes on the next pair of studs should 
be placed on the commutator, and the speed 
again taken with the same voltage and field 
current as before; this procedure being 
repeated for all pairs of adjacent brushes. 
For a direct current generator, the 
should vary directly with the voltage if a 

it i ii 1 curve is taken as described. This 
method should never be employed unl 
is impossible I" drive the machine as a gener- 
ator, asit is very difficult to read the tachom- 
eter sufficiently accurate!} 

With unload, normal voltage, and full field, 
a speed reading is taken, the brushes 
shifted so that when full load is on, the 
is not less than 5 percent, below nor more than 
'J per cent . above normal speed. Ai I he end i ij 
the speed run the machine is loaded, the 
brushes shifted if necessary, and the commu- 

■ 11 noted. 

On compound wound motors, a shunt is 
adjusted aero 

within l per cent, of the com 
rated load. Speed curves and running light 
should be taken with the eries field di 

ed. 

Run ft should be taken at hot full 

lnad peed. 

Commutating Pole Motors 

The electrical neutral on COmmuta 
p. .le motor i del. 'mined by shit tin 
brushes until the I i obtained in 



Ill' 



GENERAL ELECTRIC REVIEW 



both directions with the same value of field 
current. . This position of the rocker arm is 
marked. In double speed motors of this 
type, the neutral should be obtained at the 
high speed. 

Machines sometimes hunt with full com- 
mutating pole field, thus preventing the 
location of the neutral from being obtained. 
In this case, the field current should be 
slightly shunted, even if commutation is 
affected. Good commutation is rarely ob- 
tained in the unstable condition. 

In testing motors sent out as single units, 
of which the direction of rotation is not 
known, the electrical neutral should be 
located by shifting the brushes at no-load, 
till a position is found that will give the 
same speed in both directions of rotation. 
The fibre brush method should not be used. 
To perform this test quickly, reversing 
switches are used in the series and shunt field 
circuits. Care must be taken, when shifting 
the brushes, to avoid a dangerous rise of 
speed. 

When the proper no-load shift has been 
found for fullcommutating field, normal load is 
a] 'i lied and the commutation and speed noted. 
If the speed has increased under load or the 
commutation is not sparkless. a german 
silver shunt is used across the commutating 
field and adjusted for commutation, the speed 
for each change in the shunt being noted to 
ascertain whether the speed is decreasing 
under load. When the final shunt adjustment 
is obtained, a speed curve reading is taken and 
In pi ed and commutation in both directions 
of rotation, at no-load, full load and whatever 
overload is required arc recorded. At the 
conclusion of all tests required, while the 
machine is hot, a hot speed curve covering 
the same range of load as used in the cold 
curve is taken. In the case of two- 
machines, this curve should be taken at both 
speeds. Additional no-load and full-load 
readings should be taken at full field. If a 
falling or constant speed is obtained, and 
commutation is satisfactory, no shunt is 
ary; otherwise, a shunt must be placed 
across the commutating field and adjusted 
to give these speeds. 

Commutating pole variable speed motors 
must have the shunt in the commutating pole 
field adjusted for the highest rated 
Speed curves and running lighl hould 

be made at both ipeed limits. 

Shunt wound variable speed motors have 
the brushes set for commutation at the speed 



limits. Speed curves and running light tests 
should be made at both of these speeds. 

Some compound wound variable speed 
motors are not designed to run light; conse- 
quently, before starting, the smallest load the 
motor is designed to carry should be ascer- 
tained. Commutation should be adjusted at 
the various speeds, series full field readings 
being taken and the speed carefully recorded. 
Speed curves should be taken at the dif- 
ferent speeds; also running light, with the 
series field disconnected. 

Standard Efficiency Tests are made by 
the method of losses. 

Employing the same nomenclature as that 
used in calculating the standard efficiency of 
direct current generators, a motor efficiency 
is calculated as follows: 

C* = Cl — C 6 

Watts input \\'a=C l V l 
IFi = Core loss taken from the core loss 
curve corresponding to Vl~ CR 

Then IW = Wi+W s +W a +C* i R < +C t <Rt+ 

c- 6 k 6 + (c, v L - eve,) +c*, j?« 

+ C 2 9 7? 9 + C 2 10 /? 1 n + C 2 „/?„ 
as before. 

Watts output 11',,= W a —IW and 
II' 



£ = 



ll'„ 



Since motors are always rated according to 

horse-power output 

i Hi 

If, as in the case of direct current gener- 
ators, only a running light is taken and it is 
desired to combine the resistances of the series 
and commutating pole fields with their 
respective shunts and to combine the losses 
in the shunt field and rheostats, then 

JW r =Running light x-C^+CVk+Ci I 

+ C- l Rsf+C- l Rcf 
In the case of shunt motors 
1 II" = Running light + CV^ + C^ + CeF; 

The remarks made under the subject of 
direct current generators in reference to the 
calculation of brush friction, brush contact 
resistance and hot resistances, as well as to 
all other efficiency calculations, apply in the 
case of motors. 

It will be seen from Fig. '_'•'! that motor 
efficiencies are plotted with amperes line as 
abscissa- and per cent, ellieiency and horse- 
power output as ordinates. The horse-power 



COMMERCIAL ELECTRICAL TESTING 



1 1 3 



curve should be produced to intersect the 
axis of X at running light amperes line. 

For norm \i. load mi \ i run Hi.' machine 
is run under lead until il has reached constant 
temperatures, and these are then recorded. 
All series field shunt adjustments must he 
made to give the required regulation at the 
specified load. 

For overload heat run the machine is 
brought to normal load temperatures and the 
required overload is then applied for the 
specified time and the temperatures recorded. 

Direct Current Series and Railway Motors 

The principal type of series motor is the 
railway motor. Other types, however, are 

no 



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Fig. 23 

Efficiency and Losses on a 70 h.p.. 6 Pole. 850 R.P.M. 

500 Volt D.C. Motor 

(Plotted to values of Table IX. February Review] 

built for ase with hoists, air compressors, 
pumps, etc. As all these motors an di igned 



for intermil tent service, the test, unless i 

wise specified, i hour run al full load, 

with the brushes sel on the neutral point. 
The load must never be takei 1 1 rie mo1 or 

unless the armature circuit is first opened, 
otherwise the motor will run away. For the 
same reason a series motor should alwa; be 
started under load. All running light tests 
musl therefore be made with the field epa 
rately excited. 

As the tests on railway motoi very 

complete and the general method applies to 
tests on any series motor, those on railway 
motors will be discussed more or Jess in di tail 
Hot and cold re i tance mu I be taken 
on all railway motors and high potential 
applied both while the motor is cold and hot. 

General tests consist of sufficient prelim- 
inary tests to warrant engineering approval 
or disapproval for production. It is impos- 
sible to definitely define the heading, since 
the tests may include only a few minor 
or they may include complete and special 
tests. For instance, il may be necessary to 
make slight changes in either the construc- 
tion or design of a standard motor in order 
that it may meet special requirements. After 
these changes have been made, tests are 
conducted to make sure that the motor will 
meet sucji conditions satisfactorily. These 
tests arc included under general tests, and if 
after completion they are found to be satis- 
factory, engineering approval is given for the 
production of the machine in question. 

Complete tests consist of special ti 
thermal characteristics, commutation and 
input-output. With the exception of com- 
mutation, the other tests under this heading 
will lie considered separately. 

i lommutating I ests on scries railway motor 
should be made by holding normal voltage 
and operating the machine a1 loads varying 
from 33$ per cenl . to 200 per :en1 .no 
load. 

On series commutating pole motor . intei 
ruption tests are taken. The ;e t< I co 
in opening and closing the motor circuit 
while the machine is running at various loads 
and peeds. The machine should stand 
tesl wit houl arcing over at line volta 

high as 125 per cent, normal. The loads are 

varied from :;:;', pei cent to 't' 11 
normal. Mill motor are tested for com- 
mutation l>y suddi the din 
i .1 rot a1 ion under \ ari< ius lo 

I )evelopmi nl tesl consist ol ;eneral 
and pecial ' and an 



114 



GENERAL ELECTRIC REVIEW 



entirely new type of machine is being devel- 
oped. 

Special tests consist of speed curves, core 
loss, and saturation tests. 



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Fig. 24 
Core Loss and Speed Curve of a 50 H.P., 



500 Volt Railway Motor 

In taking a speed curve two similar motors 
are placed on a testing stand and the pinion 
ach is meshed in the same gear mounted 
on a shaft. One motor drives the other as a 
separately excited generator and is run loaded 
until the motor is heated to about 50° C. rise. 
The speed curve is then taken on the motor 

ating in firsl one direction and then the 
other, the voltage being held constant. The 
resistances of armature and field should be 
measured both before and after taking the 
curve. 

Core loss should be taken by the belted 
method, as on any other machine, except that 
the icst should be made at about five speeds. 
(Fig. 24.) The lowest speed should correspond 
to about 17") per cent, full load amperes 
(taken from speed curves) and the highi 
al about 200 per cent, full load speed. During 
this test the machine is separately excited. 

A saturation curve may be taken on a 
series motor just as on any other machine by 
separately exciting the field. Saturation 
curves at different speeds may be obtained 
from data taken during the core loss test. 

The speed curves, core losses and saturation 
arc calculated as previously explained. The 



speed curves and core losses should be plotted 
on the same sheet against amperes line as 
abscissas and revolutions per minute and watts 
as ordinates. From these two sets of curves 
another curve can be developed, which 
will give the core loss of the motor at 
any speed or current. 

The thermal characteristic should 
be obtained by making a series of 
heat runs at varying current values 
for a sufficient time to get a tem- 
perature rise of 75° C. All runs should 
be made at the same constant vol- 
tage, the current value for each run 
varying from 50 to 150 per cent, nor- 
mal. If a sufficient number of heat 
runs are taken on a sufficient number 
of motors of the same class, type and 
form, the horse-power rating for 75° 
C. rise may be obtained for any length 
of run from one-half hour to contin- 
uous running. Before starting a heat 
run, cold resistances and temperatures 
should be taken. After the motor has 
run continuously for the specified time, 
with all covers off and all openings 
unrestricted and with amperes and 
volts held constant, it is shut down, 
hot resistances measured and all tem- 
peratures taken. The results of the 
thermal heat run should be plotted, one curve 
for armature and one for field, against times 
in hours as abscissae and degrees centigrade 
rise as ordinates. Lines should be drawn 
through zero and the plotted points corre- 
sponding to the different loads, the intersec- 



200 240 



giving the respective values of time that the 
motor takes to attain 75 degrees rise with that 
load. From these curves another curve should 
be plotted with time as abscissae and amperes 
load as ordinates. This is an ampere-time 
curve for 75 C. rise. On the same sheet 
on which the ampere-time curve is plotted, a 
curve should be drawn with time as abscissa' 
and horse-power as ordinates, the horse-power 
being calculated from the standard 75° C. 
characteristics. iFig. 25.") 

In taking a load running test, as in the 
speed curve test, two motors are geared to- 
gether on the same shaft (Fig. 26), one 
running as a motor at the rated voltage and 
full load current and driving the other as a 
separately excited generator. The separately 
excited field of the generator is in series with 
the motor field, thus giving normal full load 
excitation. The armature of the generator is 



COMMERCIAL ELECTRICAL TESTING 



115 



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Fig. 25 
Thermal Characteristics of a 75 H.P., 600 1200 Volt Railway 

connected to a water box, the resistance of 
which is varied until full load on the motor is 
obtained. The run is made for one hour, 
after which temperatures are taken. 

Resistances arc measured and high potential 
applied both before and after the test and 
before starting. The speed should be checked 
in both directions of rotation. 

One out of every fifty of all types of motors 
should receive the one hour load run. All 000 
volt commutating pole motors, with the 
exception of those receiving the one hour 
load run, should be run under load for ten 
minutes in each direction of rotation. Other 
motors the characteristics of which arc well 
established should receive "commercial tests". 

Commercial tests consist in running a motor 
light for a short period. It is the practice to 
run four motors in parallel, the fields being 
connected in series and separately excited by 
a current equal to the full load current of the 
motor. (Fig. 27.) 

With normal voltage held oust ant across 
the armatures, the motors are run lighl for 
ten minutes in each direction of rotation, 



readings of speed, and armature and 
field currents being recorded. 

With rated voltage across the moi 
the fields should be weakened until 
about twice normal speed is attained. 
Under these conditions the machine 
should be run in each direction for five 
minutes, the same readings as listed 
above being taken. 

Resistance measurements and high 
potential te ts must be made before 
and after this test. 

Care must be taken that the re- 
sistance and speed at 25 degrees C. 
come within the prescribed limits already 
mentioned. 

On all series motors, with the exception 
of railway motors, standard efficiency 
tests are made by the method of losses 
and the calculation of the efficiency is 
identical with that for any other motor. 
In this case, of course, amperes arma- 
ture equal amperes line. 

In making an input-output test the 
motors are -eared and connected as for 
the load heat run and are usually run 
under full load for one hour up to ordi- 
nary working ten peratures to get the 
bearings in good running condition. 
Before the load is put on, careful meas- 
urements of the armature and field resist- 
ance of the motor and of the armature 
of the generator are taken by the drop in poten- 
tial method. Three different measurem 
should be made of each, with as many different 
values of current near normal load current. 



1 




Motor 1 
"j 
















§- Generator 












Fig 26 
Connections for Load R -inning Test on Ruilwuy Motors 



110 



CEXERAL ELECTRIC REVIEW 



Booster 




WaterBox 
ToStop "^p .F/e/J/ F/?/</z F/WJj fiekf4\ 



Fig. 2 7 
Connections for Running Light on Railway Motor 



Holding normal voltage constant, 12 or 15 
different loads ranging from as low as possible 

to L50 per cent, load should be put on, the 
directio itation being such that the motor 

tends to Lift from its hearings. Readings at 
eai i load should be taken of the amperes, 
voll i armature and speed of the motor, and 
res and volts armature of the generator. 
The direction of rotation should then be 
changed and several cheek points taken in 
d and amperes, after which the machine 
should be shut down and hot resistance 
measurements made. 



1300 
1200 



I 

IOOO /oo 



IIOO 



Table X and Fig. 28 show the 
hod of working and plotting the 
data obtained from the input-output 
test. Unless otherwise specified, the 
tractive effort and miles per hour 
are calculated for -'Jo in. wheels. The 
f6rmula? used are: 

Miles per hour = 

R.p.m.X diam. of wheels in inches X ~ 

Gear ratio X 1056 

Traction effort = 

Amps. X voll ■ efficiency X 252 

Miles per hourXSOO 

The gear ratio is that between 
the gear and pinion. 

From these characteristics new ones 
should be plotted, as shown in Fig. 29, 
the C'-R being corrected for 75° C. 

















































































































\ 




















































\ 






















































\ 




















































\ 






















































S 


















































\ 








































%Cc 


V 


"Z 


?3S ' 










S-JS?"— 
















-f 


%iJtr~~ 


mf* 


\ fr/ct/on 


































X 


^ 


























V 


1 








































,r 
















~- 


<_- 


- 









































































































900 30 



O -4C SO /20 /60 ZOO 340 

Amperes 

Fig. 28 
Input-output Curves for a 75 H.P.. 600 Volt Railway Motor 



TABLE X 

SPEED, TRACTIVE EFFORT AND EFFICIENCY OF A 100 H.P. 600 V. RAILWAY MOTOR 

















Miles per 










C*R 


Core 
Loss 


Gear- 
Friction 


Effici- 
ency 


Hour on 

33* 
Wheels 








five 
Effort 






Amp?. 








Ratio 










1 7 




30.0 


63 


I.VO 




ooo 




Ill 


170 


600 




60 


2.5 


4.1 


l in 


79.4 


35.4 


IH7 


600 




Sll 


:;.:; 


3.4 


9.0 


■ 


29.6 


687 


(Kill 








3.0 


7.5 


85.3 


26.2 


984 


600 




120 


5.0 


2.6 


6.5 


85.9 


23.8 


1310 


ui in 




140 


5.9 


2.3 


5.7 


86 l 


22.5 


1615 






160 


6.7 


2.1 


5.0 


86.2 


21.3 


I960 


600 






8.4 


1.8 


5.0 


84.8 


19 5 


2630 


r,i in 




240 


lii.n 




:,ii 


83.5 


18.1 


3350 


tii in 


■sat 


280 


11.7 






82.0 


17.2 


nun 


tarn i 










75°C. 


Arm 
















.107 


Exciting I 


field 














.076 


1 












.050 


Brush ' 


itacl 














.017 


Tot 


L'.Mi 



COMMERCIAL ELECTRICAL TESTING 



117 









TABLE 


XI 








INPUT-OUTPUT OF 


A 100 H.P., 


600 V. RAILWAY MO 


TOR 








Volts 


. ii || | 




600 


600 




Amps. 
R.P.M. 






60.5 


M| 


134 




249 








1216 


935 


790 


7i in 


610 


o 


\\ alts Input .... 






361 


56400 


80400 


106800 


149200 


o * 


,, .,, Arm. -(-Brushes 

L K . +Exc. Fld.+Comm. Field 
















s 






935 




1590 


8100 


15800 




(A)=Watts C-'R 






35365 


541 in 


75810 


98700 


133400 




(A) -(Core Loss X Fnc.) = Output 






29382 


18180 


69410 


90755 


L 23150 




Efficiency 








85. i 




85.0 


82 5 


1 Volts 


602 


592 


581 1 


551 


522 


o I Amps 




385 


70 




142.5 


203 


a W atts 




231S ) 


II 100 


61 150 


79400 


106000 


v ,-.,, ' Arm. -(-Brush . 
Si +Comm. Field 




248 


821 1 


I860 


3410 




B) Watts + C-R 




2339S 


12220 


63010 


82810 


111". 


1 (A -B) -=-2= Core Loss X Friction (1 M 

I 


ach.) 5983 


.-.'.mil 


6400 


7945 


10250 



K 



Armature 
Exciting Field 
Comm. Field . 
Brush Contact 



Total 



.1082 
.0792 
.0522 

.11170 



.2566 



Generator 


.1015 


.0492 


.017(1 






.1H77 



SOOO SO /OO 






-3 



14000 )>40 60 



<S ?> .ft 



I* 



^ZOOO^.20^40 

S/ooo^ 



10 20 



■o 

















1 


















































, 














































7Zz 


1 ' 


rifc£ 


^_ 










































•ij 


°arA 


' Ct/t 


']■ 














































































































































































































































A 






















































,tf 


1/ 






















/ 
































\iM 






















~ 






























fir 


,« 




























- 


/ 






























Af/A 


t» 


" 


_ 


-■> 


U7 


f— 






































































































































































































































































































































































, 





































ISO 'SO 

4/TJOeres 



Fig 29 
Speed, Tractive Effort. Efficiency on a 75 HP. 600 Volt Railway Motor 



rise, and the gear loss assumed a 5 per cent, 
ai lull load. If the gear loss derived from 
test has to be changed at full load, it should 
be changed in the same ratio throughout tin- 
curve. (See Table XI. 



Cooling off tests arc made by 
running the motor under full l< 
with covers off, for one hour, 
shutting down and reading tem- 
peratures as the machine < 
down. Por the first hour after 
the machine is shut down, the 
temperatures of the following 
parts are read every fifteen min- 
utes: armature, commuta 
field, frame, air in the motor, 
ami room. After the fir i hour 
temperatures should be taken 
every half hour until the temp 
lure of 1 he liol test pari is nol 

i than 25 degree C 
the surrounding atmosphere. 

The iv uli , .; the cooling 
off test should be plotted to 

time as abscissas and di 

ordinates. Thi curvi for armature, field, 
llUtator, frame, and air in the motor. 

should all be plotted on one 



2SO 



lis 



GENERAL ELECTRIC REVIEW 



THE JOHNSONVILLE HYDRO-ELECTRIC DEVELOPMENT OF 
THE SCHENECTADY POWER COMPANY 

By John Liston 



The rapidly extending use of electricity, 
especially in industrial applications, together 
with the high efficiencies now obtained in 
water wheels and generators, have combined 
to stimulate the development of those water 
powers affording either high heads or great 
volume wherever they have been found to be 
within practicable transmission distance of 
large centers of population. 

As the field for the construction of larger 



spillway dam constructed primarily to pro- 
vide additional storage water for a larger 
power house at Schaghticoke, X. V., which 
was described in the April, 1909, issue of the 
General Electric Review. The Schaghti- 
coke plant utilizes a head of 150 ft. for gener- 
ating 12,000 kw., which is transmitted on 
twin circuit steel towers at 30,000 volts, 
three-phase, 40 cycles, to Schenectady, X. Y.. 
a distance of 21 miles. 




General view of dam and power station during construction, showing turbine 
casing installed in north flume 



hydro-electric plants becomes restricted, the 
small power station utilizing low or variable 
heads and designed either as an auxiliary to 
the larger plants or for the independent 
generation and distribution of electrical 
energy, becomes of increasing importance to 
the engineering fraternity. 

In the Eastern States where the larger 
power sites have been to a great extent either 
developed or pre-empted, the construction of 
small power stations is already becoming an 
important factor in the future ol hydro- 
electric development. 

The Johnsonville power station on the 
Hoosic River is located at one end of a 



Some water storage is secured by the dam 
at Schaghticoke, back of which an area of 
1 15 aires is flooded, giving a capacity of 1 1 
million cu. ft., but the main reservoir is 
at Johnsonville, as indicated above. The 
relative location of these dams and that of 
the transmission line connecting the two 
inns is shown in Fig. 4. 

The pond back of the Schaghticoke dam 
is sufficient to hold one day's supply of watei 
and insure the operation of the plant at 
any load factor, but does not provide suf- 
ficient storage capacity to carry the plant 
over periods of low water. It was therefore 
<h, ided to construct another dam, at a point 



< 



THE JOHNSOWILLE HYDRO-ELECTRIC DEVELOPMENT 



19 



about 5 miles up the stream. This dam is 
located at Johnson ville, X. Y., about 15 
miles northeast of the city of Troy, the 
drainage area of the Hoosic vallev back of 
this point being about 550 square miles. 
The new dam backs the water up stream f< >r a 



The Johnsonvillc dam (see Fig. 1) runs 
approximately north and south at right 
angles to the Sow of the river, and is located 
just above an earlier timber dam which was 
formerly utilized for power to drive a local 
mill. In exchange for the cession of riparian 







1 




H i 






«^^i* 














>i. 







High water during construction, showing water passing over the unfinished 
sections of the dam spillway 



distance of 5 miles to the town of Buskirk, 
thereby flooding an area of 850 acres and 
giving an additional storage capacity of 332 
million cu. ft. This, added to the pondage 
originally provided, gives a total available 
water storage capacity of 376 million cu. ft., 
or sufficient to supply a flow of 250 cu. ft. per 
sec. continuously for a period of 20 days. 



Dotted- 




rights, the mill has been provided with motor 
drive and receives current from the new 
generating station. 

The development comprises a power house 
and sluice gates located on the north shore 
at the end of a spillway dam which extends 
to the south shore and ends in a heavy mason- 
ry abutment. This abutment is extended up 




Spilliaoy S30 a 







Pig 1 

Genernl plan of masonry construction 
at Johnsonvillc 






120 



GENERAL ELECTRIC REVIEW 



stream from the dam for a short distance in a 
ht line, while below the dam it cun 

wards the center of the stream, thereby de- 

flecting the water from that portion of the 

south shore immediately below the dam and 

ting t he bank from erosion at that point, 




Tail race and sluice gate diverting wall during construction 

even in times of maximum flood. In this way 
it prevents injury to the mill buildings, 
which are kx ated 120 feet below the new dam 
and b< side the old crib dam already referred 
to. 

The north shore of the river is clay hard pan 
but the dam rests on bed rock, undercut for 
its entire length. The south shore, however, 
is covered to a considerable depth with soil, 
and in order to prevent seepage around 
end of the dam, a concrete core wall 
180 ft. long was constructed, running 
on Led rock from the abutment al 
the end of the dam hack to the high 
gr< iund, a hown in Pig. 1. The c< ire 
wall has a maximum height of 25 ft., 
and is covered by an earth em- 
bankment. 

The dam is made of solid eon 
and is built up in eleven sections 
with expansion joints every 50 ft. ; il 
is of the ogee type with a total spill- 
way length of .Y;i) ft., a maximum 
height of in ft., and ii greati 
thickness al the base, of about 30 ft. 
Both the height and thickness of the 
dam diminish near 
where the river lied is higher. 

The surface of the reservoir can 
he raised :! ft . ' eans of flash 

Is, the cresl of the dam being pro\ ided 
with brass tubes sunk ii in. into the c tncrete 
and serving as sockets for the dashboard rods. 

At tlie north shore end of the dam, I sluice 
gates and an ice chute are located. The 



sluice gate masonry is of concrete having a 
maximum thickness of 38 ft. at the base and 
provided with heavy buttresses on the down 
stream side. 

The gates are of cast iron and are ordinarily 
operated through gearing by a 10 h.p. moti ir, 
which is coupled to one gate at a time by 
means of an automatic selector cut-out and 
a mechanical clutch. 

To prevent injury to the apparatus the mo- 
tor is controlled by a panel board located 
in the power house and equipped with 
circuit breakers and reversing contactor-, 
so that when a gate strikes bottom the motor 
is automatically cut out of circuit. Hand- 
wheels are provided for use in the event of 
injury to the motor, and all the gate control- 
ling mechanism is housed in a concrete 
chamber which caps the gate masonry and 
is at a sufficient elevation above the crest of 
the dam to prevent injury during floods. 

The gate openings are Oft. by !• ft. each, and 
with the reservoir full their combined capacity 
is solid cu. ft. per sec. The gate masonry is 
grooved for stop logs so that the openings may 
he shut off and the gates inspected or repaired. 

Between the sluice gates and the power 
house is a log and ice chute, having its sill 
3 ft. below the crest of the dam; when 
not in service it is closed by means of 2 sets of 
stop logs set in side grooves. Running 
diagonally up stream from the ice chute to 
the north shore is a deflecting curtain wall 




Sluice gate operating mechanism 

about 160 ft. long, under which are .". sub- 
merged openings that admit the water to 
the forebay. The top of this wall is 3 ft. 
above high water, and the inlets are ."> ft. 
below the crest of the dam and 2 ft. below the 



THE JOHNSONVILLE HYDRO-ELECTRIC DEVELOPMEN1 



L21 



sill of the ice chute, so that floating ice, logs 
and other debris are diverted to the ice 
chute. The forebay portion of the wall 
has tu withstand ice pressure from both side . 



are of reinforced concrete I ft. thick, and 
designed to withstand the thrust of the 
water with both flumes full, or one full and the 
other empty. The reinforcing is carried back 




View looking up stream showing finished power house and sluice gate masonry 



and is therefore reinforced in both vertical 
faces and braced by two reinforced concrete 
beams spanning the triangular shaped fore- 
bay and tying the deflecting wall to the 
retaining wall which supports the clay hard 
pan bank of the north shore. 



to the north shore retaining wall on one side 
and to the dam on the other, in order to give t he 
necessary stability. The curtain wall over 
the intake gate is located directly across th- 
intake and supports the upper part of the 
flume gate framework; it is :! ft. thick at the 





View looking down stream, showing dam equipped with flash boards and intake to forebay 



The water from the forebay, after passing 
through screens and gates and ui. ler a curtain 
wall, enters two flumes, each 20i ft. wide, 
27', ft. long, and '■'>'> ft. high;the walls of which 



bop and extends downward from the 'leek of 
the Hume for 17 ft. 

The flume gates are made of structural 
steel, each approximately is ft. high and 21 ft . 



122 



GENERAL ELECTRIC REVIEW 



wide; they operate in angle iron seats set in 
the concrete sides and owing to their great size 
have additional support in the form of twosteel 
beams for each gate, which extend vertically 
from the floor of the flumes to a concrete 
girder at the bottom of the curtain wall. 
Each gate weighs about 7 tons and is raised 
or lowered bv means of two steel screws 



amount of water which is admitted to the 
wheels is controlled by wicket gates mounted 
in a ring around the runners and operated by 
a common rotating shaft which is geared to 
the governor in the generating room. 

When operating under a 35 ft. head the 
turbines develop 3000 h.p., and when the 
water is drawn down to a 24 ft. head the out- 



\ 



fcir 




. . • ;' • ■ ' ■ ' ■ ' > ' .-..- ':' •• ■'.•'•-.' ' .•-' i >/ ' . ; *. •. .- . .;' ■ - ' , *rr"^Oi 



Fig. 2. Sectional view of power house and flume showing compact 
arrangement of the equipment 



connected to a pair of handwheel operated 
hoisting stands at the top of the flumes. In 
order to facilitate the raising of tin.' | 
2 I inch by-pass valves arc- used to first fill the 
flumes and thus balance the water pressure. 

As the Johnsonvillc dam is primarily 
intended to store water for the Schaghticoke 
power house, it is evident that the auxiliary 
power plant ai the dam must frequently work 
under widely varying heads, .and the turbines 
are there! igned to •" under 

heads ranging from 24 ft. to 3!) ft. 

In each flume there is mounted s ">7 inch 
double runner reaction turbine of the hor- 
izontal Franris type, as shown in Figs. 2 and 3. 
The wheels discharge into a common draft 
chest located between the runners and the 



put is reduced to 17.">0 h.p.; the speed, 
however, remaining constant at 150 r.p.m. 

The walls which separate the wheel pits 
from the generating room are I ft. thick and 
made of reinforced concrete; the turbine shafts 
entering the power house through cast-iron 
watertight bulkheads, ring concreted in the 
wall. Each turbine is controlled by a stand- 
ard "Lombard" oil pressure governor, belt 
connected to the generator shaft and geared 
e wicket shaft, as shown in Fig. 3. 
The governor is ordinarily automatic in op- 
eration, but hand control is provided for in 
the event of injury to the governing mech- 
anism. 

A tubular glass water gauge located in the 
power house and set vertically between the 



THE JOHNSONVILLE HYDRO-ELECTRIC DEVELOPMENT 



123 



governors at all times indicates the operating 
head. 

The power house is constructed of rein- 
forced concrete and steel, the approximate 
inside dimensions being SO ft. long. 30 ft. 
wide, and 40 ft. high, the general arrangement 
of the interior being as shown in Figs. 2 and 3. 

Although the capacity of this station is only 
3600 kw., the construction throughout is of 
the most substantial nature and everv device 



ment, and the high tension wiring. All the 
low tension equipment is located in a brick 
walled compartment beneath the switchboard 

gallery. 

A l.")-ton overhead traveling crane is 
included in the station equipment, and there 
is also a portable motor-driven air com- 
pressor set for cleaning the machinery; the 
direct current for the motor being supplied 
bv the exciters. 



T T 



^ £ 




:"■:■;/::•■■ : : ■^M?-,X$.>,3&mZ 




1 U 




«-> - -* * 



-;-■'■■■ ■ ■ ■ >■■ ■ ■••■ ■ • < (-!i ■■■ /-■ ■■ — 



• ~xlJ 




■■ __} ■ ■ ;_!/ 



Fig. 3. Flan of power house and flumes showing the location of 
turbines, generators and governors 



of approved value for maintaining high 
efficiency and uninterrupted service has been 
installed. The two transformers are located 
at the north end in separate fireproof 
compartments with steel curtain doors, and 
the switchboard is erected on a gallery 
between these compartments. Ab( ve this 
gallery is a floor extending across the building 
on which are located the generator and line 
motor operated oil switches, instrument trans- 
formers, aluminum lightning arrester equip- 



After leaving the turbine draft tubes the 
water passes through -1 tail race opening 
arched walls of which support the floor of 
the generator room. Beyond these, and ex- 
tending down stream from the powi 
are two heavy concrete 
about 100 ft. long with a maximum I 
of 2 1 It ., which forms 
Lank of the river al this point and protec 
road to the power house from the effects of 
ero ion. A lower wall aboul 120 ft. long, and 



124 



GENERAL ELECTRIC REVIEW 



curving toward the center of the stream, 
serves to divert the flow from the ice chute 
and sluice gates away from the tail race. 




One of the two 1800 Kw. Type ATB 3-phase 40 cycle 4400 volt 
with self-contained exciter 

The total amount of excavation for the 
c instruction of the dam was about 6500 cu. 
yds. of earth and rock, and the con- 
crete used in the main dam totals 
about 12,0110 cu. yds., more than 1600 
cu. yds. being used in the gate section 
alone. Work was begun in June, 
I'. 108, and current was first sent over 
the line in June, L909. 

The accompanying illustrations 
show the compact arrangement of ma- 
chinery and controlling apparatus 
which ran now be realized in even 
iii' smallest modern hydro-electric 
plant, and the efficiem ii which may 
obtained in the operation of 
'■ted generators and 
transformers are indicated bytl 
lowing description of the apparatus 
installed at Johnson ville. 

The generator equipment consists 
oi two 1800 kw., three-phase, 10 
cycle, lioo volt generators deliver- 
ing 237 amperes at 150 r.p.m., direct 
coupled to the turbine shafts. The 
machines are of the horizontal shaft. 
two-bearing, revolving field type, de- 
signed for water-wheel drive and ar< 
provided with an exciter mounted on 
the generator shaft between tl 
mature and the collector rings. The 
field windings are tested for 1500 volts 



and the armature windings fur 9000 volts. 

The temperature guarantee for full load 

run of two hours, at 100 per cent, power 
factor, is -10 deg. C. rise, and at 
25 per cent, overload, oo deg. C 
these guarantees being based on a 
room temperature of 25 deg. C. The 
machines will operate at 2000 kw., 
90 per cent, power factor for two hours 
with a temperature rise not exceeding 
")."> deg. C. The generators have the 
following efficiencies: full load, 95 
per cent.; % load, 94 per cent.; J^ 
load, 92 per cent. These efficiencies 
arc based on 100 per cent, power 
factor, and the regulation under these 
conditions is within S per cent. 

The total weight of combined gen- 
erator and exciter is 1 10, 200 pounds, 
and the fly-wheel effect 72(3,000 i WR 2 ). 
The armature windings are all "Y" 
connected, with the neutral brought 
to the terminal block, and the gen- 

ators erators are operated in parallel with 
those in the Schaghticoke station. 
In these machines the mechanical design 

is such that thev mav be run momentarily at 




Interior view showing north end of power house and the general arrangement 
of transformer cells, switchboard, and high tension gallery 



THE JOHNSONVILLE HYDRO-ELECTRIC DEVELOPMENT 



1 25 



300 r.p.m. (or double speed) without d 
"i" any displacement of parts, or other injury. 
The generators are controlled by mea 
Geld rheostats arranged for magnetic operation 
from tht' switchboard, from which point the 
turbine governors can also be 
controlled. 

The exciter equipment com 
prises two 8 pole, 60 kw. ex- 
citers operating at 150 r.p.m. 
and delivering a full load current 
of 480 amperes at L25 volts. 
The exciter is compound wound 
and test cm 1 to deliver the same 
voltage at full load as at no-load, 
the series field being provided 
with a short circuiting switch for 
cutting it out of circuit. The 
exciters arc also guaranteed 
to withstand temporary oper- 
ation at double soced. I-"aeh 
exciter has sufficient capacity t<> 
excite both alternators and op- 
crate the auxiliary machinery. 

Two40 cycle, 1800 kw., 32000 
I Kill volt transformers are used, 
requiring 1300 gallons of oil 
and a water circulation of II gallons per 
minute. The water for cooling is piped 
to the transformers from the wheel pits, 
and the cooling coils are tested to withstand 
a pressure of 250 lbs. per sq. inch. The 
temperature rise for a full load run of 2d hours 
does not exceed .'!.") deg. C, while a 25 per 
cent, overload maintained for the same length 
of time will not produce a greater rise than 55 
deg. C. 



%mwm-^ 



transformer, including oil, i 38,000 pounds. 
Each unit is able to withstand an instan- 

us -lion circuit at its high potential 

terminals when connected to the 3600 lew. of 
generator cap. r the total normal 




Fig. 4. The Johnsonville-Schaghticoke Transmission Line 




A complete turbine unit showing wicket gate arrangeme 
controlling inflow of the water 

The regulation on non-inductiv loads is 1..") 
per cent, and with 80 per cent, power factor 
it is :;.[i per cent. The total weighl oi each 



capacity of the power house) without dis- 
placement oi or damage to any of its parts. 

Practically the entire output of the John- 
sonville station is transmitted at 32,000 volts, 
three-phase, m cycles, to the Schaghticoke 
power house over a single circuit line of light 
structural galvanized steel towers 5.8 miles 
long. It is there tied in with the circuits 
running to Schenectady. 

A short 1(1(1(1 volt line extends aero 
the ri\ er to J< hnsonville on 
the smith batik, where it 
as a local feeder for a mill 
consuming about L50 h.p., 
and will also in the near fut lire 
supply a lighting circuit for 
[ohn tonville and Va [ley 
Falls. 

In the event of shut-down 

at Jo ille, for arc. cau :e, 

current can be fed back from 
Schaghticoke to supply 1' 

requi and for the 

eration of the tation aux- 
iliaries. 

The conductors leave the 
power hou < through perft ira 
v indi iv i in i he high tei 
i . the electrolytic lightning arrester 
being located in d the 






nt for 

led 

galle 

cell , 



126 



GENERAL ELECTRIC REVIEW 



horn gaps and discharging mechanism on the 
roof. 

All of the towers, 54 in number, are of the 
same structural form as the ones illustrated 
herewith, and the average spacing is between 
500 and liOO feet. Thev will withstand a side 




The end of the line showing transmission towers 

turning angle on the hillside back of the Schagh- 

ticoke power house 



strain of 3000 pounds at the cross arm 47 
ft. from the ground, arc 16 ft. square at the 
base, and weigh about 1500 pounds. The 
conductors arc No. 2 B.&S. solid copper wire 
spaced 5 ft. 6 in. apart, and the lightning 
guard wire is No. 2 B.W.G. galvanized iron, 
running along the peaks of the towers 2 ft. 
9 in. above the cross arms. On account of 
the lightness of the conductors no attempt 
was made to string the line at high tension. 
The conductors were, therefore, run at 600 
pounds average tension, corresponding to 
about 18 ft. sag for standard spacing. 

Heavy towers of the same general dimen- 
sions are used to negotiate angles in the line, 



and General Electric multiple disc suspension 
and strain insulators have been used through- 
out. 

The entire development was designed and 
constructed by Messrs. Vide, Blackwell & 
Buck of Xcw York, the hydraulic machinery 
was supplied by S. Morgan Smith Company 
of York, Pa., and all the electrical apparatus 
by the General Electric Company. 

In conclusion, it might be well to note the 
benefits actually derived from the operation 
of this auxiliary power plant, located at 
what is practically an impounding dam 
primarily intended to supply additional 
storage water for a larger existing station. 
We find that at the present load factor of 




Standard transmission tower used between 
Johnsonville and Schaghticoke 



50 per cent, the total output of both stations 
during an average year is equal to 67,600,000 
kw. hr., and of this total 13,120,000 kw. hr. 
is delivered by the Johnsonville power house. 



127 



STORE LIGHTING 

By F. L. Heaiv 



Among the many rapid strides which have 
been made in illuminating engineering, 
perhaps no one particular branch of the art 
has received more careful attention than the 
artificial lighting of stores. 

The chief reason for this was the necessity 
of overcoming the color distortion which was 
characteristic of certain forms of artificial 
illuminants. 

Until recently the ordinary enclosed arc- 
lamp has best served the purpose very well, 
but it remained for the intensified arc lamp to 



was used, as when daylight was employed for 

lighting, due to the fact that the goods did n< >t 
show up as well under the former as under the 
latter. 

Determined to remedy this if possible, a 
series of exhaustive tests was conducted on 
all the latest forms of illuminants and so- 
called white lights, with the result that the 
intensified arc lamp, although the last one 
tried, was immediately chosen, as its true 
daylight qualities and superiority over any 
other illuminant were at once appreciated. 




Fig. 1. Main Floor of C. G. Gunther Sons Co., New York City 
Lighted by General Electric Intensified Arc Lamps 



provide that white light and soft and even 
illumination to which the eye is so accustomed. 

A striking illustration of the valui 
intensified are lamps for store lighting is 
furnished by the new store of ('. G. (iunthcr 
Sons Co., of Fifth Ave., New York City, 
dealers in high grade furs. When changing 
their headquarters from the old down-town 
store to the new building, the utmosl 'arc was 
taken to obtain the best available equipmenl 
for a rapidly extending busini Past ex- 

perience had taught them that sales were 
seldom, if ever, as good when artificial lighl 



That these lamps fully come up to cxpecta- 
, is realized on enti ring this new store 
mi Fifth Avenue, where they arc installed 
throughout . 

Tin main lloor has a very high ceiling 
which gives thi large displa room a 
modious appearance. The finish is a 
dark brown walnut ami it is doubtful if a 
betl er backgri iund c mid !"■ ob1 ained for the 
,], jpla ■ .1! ur and hat On t he upper 

flour arc other reception and fitting rooms, 
in which an elaborate line of complefc 
ments and fui 



128 



GENERAL ELECTRIC REVIEW 





Figs. 2 and 3. R. H. Stearns, Boston. Mass , Lighted by 
General Electric Intensified Arc Lamps 



STORE LIGHTING 



[29 



After a general survey of the store, atten- 
tion is naturally turned to the lighting 
scheme, which accords so well with the 
highest type of store furnishing, and it is 
then that the intensified arc lamp is really 
appreciated at its true worth, as the illumi- 
nation is particularly effective. Men in the 
fur business state that people will not trust 
to artificial light in selecting furs, as under a 
light of imperfect color, the finest grades of 
sable and other costly skins lose their lustre 
and have the flat unattractive appearance of 



source of light comes within the range of 
vision. Another point worthy of mention is 
the steadiness of the light. There is no 
apparent wandering of the arc, no flickering. 
One wonders if the lamps are in reality arc 
lamps. 

Although efficiency was somewhat of a 
secondary consideration, the Gunther firm 
is ready to admit that it is getting a 
great deal more light at a lower cost than 
it was in the old store. The Lamps 
themselves are particularly attractive in 




Fig. 4. Second Floor, C. G. Gunther Sons Co., New York City 



skins many times cheaper. This is the 
point — the ordinary artificial illuminant does 
not give the fur dealer a fair chance to show 
his goods to advantage, and what is equally 
important, the buyer is not able to distinguish 
the high grade furs from the low, or even to 
match skins of apparently the same color. 
The Gunther people say that the light from 
the intensified arc lamp is the nearest ap- 
proach to daylight that they have ever seen. 
The light' itself is exceptionally well 
diffused; there is not a bit of glare in the Store 
— just a soft even light throughout. Tin 
excellent diffusion relieves one from the 
ordinary annoyance experienced when the 



arance, being equipped with an o 
mental casing of a very attractive design. 

A somewhat similar in rtallation, in the new 

tore of R. II. Stearns of Bo ston, Mass., is 

shown in Fig .2 and 3. Here also the intensified 

arc lamp was finally installed after a com- 

petitive tesl and, as will be noted from the 

photographs, the results are indeed very 

satisfactory. Note how all the finesse of 

expensive embroideries and imported laces 

i broughl out in all r y. The illus- 

ms do not reproduce the color effect, but 

from the detail shown, that as 

an example oJ idi J ore lighting, these lamps 

are without an equal. 



130 



GENERAL ELECTRIC REVIEW 



STARTING COMPENSATORS : 



By E. F. Gehrki ns 

Transformer Engineering Department 
General Electric Company 



Some form of starting device, the func- 
tion of which is to limit the current taken 
from the line by the motor in starting, is 



cases much higher than necessary, some 
sort of a device is usually provided to limit 
the current to a reasonable amount which 
is still sufficient to produce the torque 
necessary for starting. The starting de- 
vices at present used for this purpose may 
be classified as follows, viz.: 

Starting Compensators, 
Starting Reactances and 
Starting Resistances. 

An induction motor requires a certain 
amount of current to start, and, to obtain 
this current, since the applied voltage is 
the only factor susceptible of adjustment, 
it is immaterial, as far as the starting of 
the motor is concerned, whether this result 
is secured by means of a resistance, a re- 
actance, or a compensator; or whether the 
voltage necessary to produce this current 
is applied at once or gradually. 

The compensator, however, is used al- 
t exclusively, the reason for this being 
that for a given condition of starting, the 
current taken from the line with a com- 
pensator is always less than with either a 
resistance, or a reactance. These latter 
devices have the disadvantage of taking the 
same amount of current from the line at 
LOO per cent, voltage as they deliver to the 
motor ;.' a lower voltage, the reduction in 
the voltage being dependent upon the re- 
sistance of the device, whether ohmic or 
reactive. They therefore simply serve to 
reduce thi' current taken from the line by 
limiting it t<> the amount actually required 
by the motor to stan . 

A tarting compensator, however, con- 
of an inductive winding with taps, 

ether with a switch for connecting the 
motor thereto. By the operation of this 
device a reduced potential is impre 

m the motor to bring it up to speed. 
With thi ch in the starting position, 

the arrangement is equivalent it o 

Reprinted from G* 
•Since the above article was written, start-net compensators have been redesigned so as to incorporate a number of improve- 
ments, anil Fig. 1 does not then : \<_<\ description of the i: mpensator will, however 
i at some future date. The starting curves of the motor are not exactly correct for a motor of our present design, in that the 
new motors require a smaller starting current than thi 1. This change in the design of the motor, however, in no way 
affects the conclusions drawn from thi * hat. regardless of the design of the motor, there is no practical value in starting a motor 
■ins of a multistep compensat ecial cases. 




Fig. I. Single Tap Compensator, Type CR, Form F. 

d for alternating as well as for dir< 
eurrent motors, and tor both the induction 
and synchronous types; but, as the start- 
ing compensator is used principally in con- 
ion with the squirrel cage type of in- 
duction motor, th'' present discussion will 

er only to the various methods now in 
Use for starting this kind of machine. An 
induction motor designed to meet the best 
condition of normal operation, should have 
as low an impedance as practicable, but a 
motor of this description necessarily tal 
a very large eurrent in starting, this cur- 
rent being inversely proportional to the 
impedance; the starting torqu< nse- 

quently high, and, being in the majority of 



STARTING COMPENSATORS 



131 



a step down transformer, and the producl 
of potential times currenl on the line 
cuit is approximately equal to potential 
times current on the motor circuit. 
To illustrate: Assume thai 50 

cent, of the normal voltage is sufl 
to start the motor. With this potential, 
the motor takes one-half of the currenl 
that it would take if thrown on the line 
direct, i.e., one-fourth of the volt amperes. 
Assuming the current taken from the line 
by the motor if thrown on the line direct 
as 100, the use of a starting resistance or 
a reactance would reduce it by one-half or 
to 50, and the use of a compensator would 
reduce it by three-fourths, or to 25. 

The actual relation between the starting 
currents for a 100 h.p., 25 cycle, 440 volt 
motor, is illustrated graphically by Figs. 
No. 2 and No. 3, the former showing the 
current taken with the motor starting up 
with 100 per cent, load, and the latter with 
about i2.~> per cent. load. Both curves serve 
to show the decrease in the line current by 
the use of the compensator, but espe 
when starting the motor with no load or 
light load. 



left in a itarting position loi i ough to 
allow the motor to attain practically full 
peed. This usually requires from fr 
twenty seconds, and, at the end of that 









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Fig. 2. Starting of 1-6-100-500-440 Volt Form K Motor 
with 100 per cent. Load 
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Fig. 3. Starting of 1 6-100-500-440 Volt Form K Motor 
with 25 per cent. Load 

time, the switch should be thrown quickly 
into the running position. If the switch is 
thrown before the motor has attained 
speed, the current broken on tarting 

side, and the instantaneous currenl ial.cn 
from the line on the running side, are much 
larger than when the full time allow- 
ance is given. The latter is also the case 
if the switch is not thrown quickly, as the 
motor must necessarily drop in ipeed dur- 
ing the time the switch pas rom the 
starting to the running position. This, 
therefore, no1 onlj defeal • the purpo 
which compen ator are di igned, bul the 

ce isive current is also del rimental ti 
switch. 

Starting coi are arranged in 

one of two ways, first, o thai one reduced 
voltage may be applied to the motor ter- 
minals, and tecond, so thai several successive 
es may be o d. The for- 

mer, or mi ii the 

simpler in construction, and i 
the majority of in tallal ion The I; 
or multi-tap compensator, has advan 
tages only when the Static friction of the 



132 



GENERAL ELECTRIC REVIEW 



load varies from day to day, or for the 
starting of a synchronous motor operating 
under conditions that require very low 
starting torque and when it is desired to 




Fig. 4. Single Tap Compensator Switch with Latch 

take advantage of this condition in avoid- 
ing undue line disturbances. Under these 
conditions a comparatively low voltage is 
required for starting and bringing the syn- 
chronous motor up to synchronous speed; 
then, by adjusting the field current to each 
increase in voltage, the current taken from 
the line in passing from the starting tap 
to the full line voltage is reduced t<> a mini- 
mum. As inferred, this me tod can- 
not be used to advantage where compara- 
tively large starting torque is required, nor 
does it apply to the induction motor, in 



which machine field current adjustment is 
not possible. 

The multi-tap compensator switch is 
usually arranged so that the movement of 
the handle is continuous, starting with the 
"off" position, and passing through the suc- 
cessive steps to the full voltage position. 
This arrangement allows an operator to 
throw the switch through the starting and 
into the running position in so short an 
interval that the motor will not have had 
time to start before full voltage is applied. 
Also, because of the large number of con- 
tacts to be made at each point of the switch, 
a considerable amount of force is required 
to operate it, and, on account of the smaller 
angular distance between the various pos- 
itions, the operator is likely either to throw 
the switch too far, or to operate it so slowly 
as to cause serious burning of the contacts. 

In the single tap compensator, these 
difficulties can be entirely overcome by 
arranging the switeh so that the "off" 
position is in the center, the starting posi- 
tion at one extreme end and the running 
position at the other extreme of the throw 
of the handle. 

By arranging the switch in this way, 
the operator has a positive stop at both 
the starting and running points, and he 
will be more likely to throw the switch 
full into the proper position, and leave it 
in the starting position a greater length 
of time than if the entire operation could 
!»• completed with one sweep of the handle. 
With a compensator arranged in this manner, 
proper operation is assured by the addi- 
tion of a latch as shown in Fig. 4. 
This not only prevents the operator 
from throwing the switch into the running 
position before it has passed through the 
starting point, but also compels him to 
throw it over quickly, which reduces the 
burning of the switeh contact and also 
lessen^ tlie momentary increase in the cur- 
rent taken by the motor when thrown 
from the tap to the line direct. 

As previously stated, the design of the 
squirrel cage type of motor is such that no 
adjustment of any kind whatever can be 
made for the purpose of producing 
besl starting conditions, with the- excep- 
tion of that of the voltage applied to the 
motor terminals; and because o : the infle 
bility of the system, it is immaterial how 
this voltage is applied, the only require- 



STARTING COMPENSATORS 



133 



ment being that the voltage be sufficienl 
to give the current necessary to overcome 
the static friction of the load. As no ad- 
justment in the motor itself is possible, 
the application of any voltage below this 
is of no advantage in any way, except that 
it heats the armature winding, and by thus 
increasing the resistance, a slightly greater 



This conclusion, that there is no prac- 
tical advantage in the application of a 
gradually increasing voltage to a squirrel 
cage type of induction motor, is shown by 
the curves and is the result of a series of 
Starting tests which were taken with 
different load conditions on a 15 h.p., 60 
cycle, 220 volt, three-phase motor, and on 



















































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Fig. 5. Starting of 1-6-100-500-440 Volt Form K Motor with 100 per cent. Load, Using Multi-Tap 

Compensator, and Single Tap Compensator. Multi-Tap Compensator, 30, 40, 50, 65 and 80 

per cent. Taps; Test Indicated by Broken Line. Single Tap Compensator, 75 per cent. 

Tap; Test Indicated by Solid Line 



torque may be obtained. Furthermore, the 
characteristic of a well designed induction 
motor is such that the voltage necessary 
for starting is also sufficient to bring the 
machine to practically full speed without 
further increase, so that thi application 
of an intermediate voltage between that 
necessary to start the motor and full line 
potential is of no advantage. 



a LOO h.p., '2'} cycle. Mi) volt, three-phase 
motor, using multiple 

of the proper size 
for each machine. 

In this in\ ators 

anected in with each other 

and between the line and the motor, 
while a graphic recorder was connected in 
series with ; of the line. Six starting 



134 



GENERAL ELECTRIC REVIEW 



ti i were taken for each condition of load, 

d with the best arrangement of com- 
pensator taps, one being tested while the 
other was cut out of circuit by throwing 
its switch into the running position. 

The tests wen- taken with each com- 
pensator alternately, and the results on 
the 100 h.p. motor starting under full load 
conditions are shown in Figure 5. A 
large number of tests under different load 
conditions were taken, but these shown 
are representative, and being taken 
with a comparatively large load on the 
motor, would be better suited to show the 
advantage of the multiplicity of starting 
taps, if any existed. A study of the curves 
will show, however, that the amount of 
current taken from the line to start the 
motor under a given condition of load is 
the same regardless of whether this voltage 
is applied gradually or instantaneously. 

Attention is also called to the large cur- 
rents which the switch of a multi-tap com- 
pensator is required to break. Iivthe pres- 
ent instance, for a single start, the switch 

i required to rupture currents which 
were respectively fit), 110, 175 and 300 per 
cent, of the full load running current of 
the motor, whereas, with a single tap com- 
pensator, the maximum current to be 
broken was but a trifle over full load 
current. 

In the majority of installations of induc- 
tion motors, however, the load to be started, 
and consequently the voltage neces- 
sary to start, is approximately con- 
taut from day to day, and a single tap 
compensator, or rather one having a 
number of taps, any one of which can be 
cted for use, is ; perfectly satis- 

ai torj after I he proper tap for the par- 
ticular installation has onci been fixed upon. 

The advantage of the single tap com- 
pensator can therefore be readily appre 
eiated, as it is simpler in di ' opera- 

tion, and the desired results more likely 
to be obtained even when operated by 
inferior class of labor. The cost of main- 
tenance is also reduced as not only . 
the muni. ei- of ruptures of current decrea ed 
to a minimum, but the burning of the 
contad and their renewal are also les- 
sened, this reduction being in propor- 
tion to the deer in the er of 
contacts, and therefore tlie number of rup- 
tures oi current, and also on account 
of the breaking of a much smaller current. 



A NEW TYPE OF METER FOR 
MEASURING THE FLOW OF 
STEAM AND OTHER FLUIDS 

By A. R. Dodge 

The ever increasing demand for more 
economical generation and consumption of 
steam makes it imperative that the up-to- 
date engineer shall avail himself of every 
possible means for determining the behavior 
of apparatus that is employed for these pur- 
poses. 

For many years the electrical engineer has 
had instruments at his command by the use 
of which he could determine exactly the 
performance of the various electrical ma- 
chines. On the other hand, despite the fact 
that the utilization of steam and the science 
of steam engineering antedates the practical, 
commercial application of electricity by half 
a century or more, the steam engineer has 
been provided with no such instruments, 
and has had to content himself with the 
simple knowledge that he was generating 
enough steam to do a certain amount of work ; 
just how much steam it was that he was actu- 
ally generating he could not tell. It must 
be conceded that it is as important to measure 
the steam delivered to the prime mover as 
it is to determine the output of the electric 
generator. This point is fundamentally im- 
portant, but up to the present time there 
si ems to have been no large amount of work 
spent on the development of instruments 
which possess the desired properties of being 
easy to install and of accurately measuring 
the rate of How of steam. 

The former efforts in this direction are 
covered by two general types. 

About ten years ago a device for measuring 
steam flow was brought out in which a dia- 
phragm containing an orifice was inserted 
between flanges in the steam pipe, and the 
difference of pressure between the two sides 
i In- orifice was measured, from which 
pressure difference the amount of steam pass- 
through the orifice was known from pre- 
ilibration. No attempt was made to 
< oneri for moisture or superheat, ami there is 
a loss of steam pressure through the orn ■ 

at ordinary loads of about three poun 
which loss increases in pressure at overloads, 
limiting the output and efficiency of the steam 
distribution system. To install this device 
necessitates shutting off the steam for several 
hours; removing a section of piping and in- 



A NEW TYPE OF METER 



135 



serting a new section, together with new- 
gaskets and diaphragm in the same available 
space as was occupied by the removed see 

The second type is known as the float type 
meter and consists of a vertical spindle which 
carries a disk, actuated by the steam, an 
arrangement somewhat similar to the safety 
valve of a steam boiler with the spring re- 
moved. The more the flow of steam, the 
more the spindle will lift due to the pressure 
difference on the top and bottom. The 
spindle is connected through the stuffing box 
to an external pointer, by means of which the 
opening of the valve, and hence the amount 
of steam passing through, is known from pre- 
vious calibration. Either the disk or the 
surrounding chamber may be cylindrical, 
provided the other part is conical. 

The stuffing box is a serious objection, as the 
friction is always an appreciable amount of 
the moving force available from the steam, 
and varies over a wide range. A leakage of 
steam through the stuffing box is also apl to 
occur. These two characteristics tend to 
make the readings inaccurate. Such meters 
owing to their relatively large size and cost 
are not practical for pipes above G in. in 
diameter. 

In the meter to be described, these ob- 
jections have been eliminated an 1 an in- 
strument developed which, without the use 
of weighing tanks, scales, or other special 
apparatus, will determine the amount oi 
steam, air or other fluid flowing in a sj stem of 
piping. 

If the temperature and pressure of tru 
is a constant, the amount oi d in a 

machine or group of machines is, of course. 
proportionate to its velocit; infeetpei econd 
This velocity, therefore, constitutes a n 
of measuring this quantity if the veloci 
itself, can be measured. It is a well known 
fact that velocity i com erted into pre ur< 
by means of an inverted nozzle with prai tii J 

loss ami always under the satin 
The measure of this pressure', due in vein, [\ 
is the most reliable means we have of deter 
mining the velocity of steam in nozzle .which 
may be as high as 2500 ft. per second. 

The velocity bei u d from 

the pressure, the quantil y of tl ti is a1 

nil, e deducible. being proporl i 
above. A nuzzle plug i crewed into the pipe 

at the point where the fli i lured 

and extends diametrically aero it. This 
plug (Pig. 1 1 carries two f opening 

first or "leading et direc 



tion of flow, while the second or "trailing" 
■ i three openings near i he center 
of the pin these latter being shown in 

the figure. The steam impinging against the 
leadin i i ipenings, tel up a pre sure in 

them which is equal to the static pre are plus 
a pressure due to the- velocity head; while the 




Traili, 



im m>- 



LeadingSet 



Fig 1. Nozzle Plug 

pressure in the trailing set is equal to the 
static pressure minus a pressure due to the 
velocity head. On account of the small 
diameter of this nozzle plug, no appreciable 
drop in steam pressure is caused by its in- 
sertion in the main, even if the velocity be 
very high. 

Since the nozzle plug extends diametrical- 
ly across the main, the difference of pressure 
set up in the two sets of openings will be pro- 
portional to the mean velocity of the gas. 
This pressure difference is transmitted through 
separate longitudinal chambers to the outer 
end of the plug and from then-, by proper 
piping, to t he meter, which consists e entialb 
of a U tube of glass or metal partially filled 
with mercury (or other fluid of gr pecific 

gravity than the fluid to be m< tsured 
The difference in pressure in the leading ami 
trailing sets of openings is communicated to 
the two Li I' of the 1' tube anil can 
difference in level in the- two 1, ,, the fluid 
column. 

Meters uitable for measuring the rate of 

if -.team are calibrated to read direel ]\ 

mds per hour, whi i uring 

the rate of flow of air are i din cubic 

i if free air at a tem 

Fahrenheil . 

[1 r i di it erate the meter on 

steadj flow . uch a occui in uppl; 

ms.manu- 
facturing pro i iration i 

r installii rs are 

calibi . - 

If, hO I . the I"' <' on 

lically intermil tei a occurs 

in sin ei it flow lur- 

c, il 



136 



GENERAL ELECTRIC REVIEW 



must be recalibrated after it is installed, unless 
the arrangement of the piping permits the 
insertion of the nozzle plug at a point where 
the flow is steady. For example: where an 
engine is supplied with steam by a long pipe 
line, the nozzle plug may be inserted near 
the boiler where the flow is steady. 

No change whatever is required in the main 



fcsgjf, 




Fir. 2. Recording Steam Meter. Showing Connections to Pipe 

piping system of the station to install the 
meter; it is only necessary to drill a small 
hole in the main lor the nozzle plug. 

RECORDING FLOW METERS 

The recording flow meter for measuring 

t he rate i 'I' flow of steam is a curve drawing in- 
strument, giving an accurate recoi : he 
rate of flow in pounds per hour, in pipes of 
any diameter, at any di tempera- 
ture, pressure, or moisture. 



The meter consists of two cylindrical hollow 
cups filled to about half their height with 
mercury, and joined together at the bottom 
by a tube. This arrangement of cups and 
connecting pipe forms the L T tube, which 
is supported upon a set of knife edges about 
which it is free to move as a balance. 

Any difference of pressure in the two sets of 
openings in the nozzle plug is communicated 
to the cups through flexible steel tubing placed 
inside the case, and causes the mercury to 
rise in the left hand cup and fall in the right 
hand cup until the unbalanced columns of 
mercury exactly balance the difference in 
pressure. 

By the displacement of the mercury, the 
beam carrying the cups moves downward 
on the left hand side of the knife edges. This 
side will descend until the moment of the 
weights on the right of the knife edges exactly 
balances the moment caused by the displace- 
ment of the mercury into the left hand cup. 
The motion of the balancing beam is multi- 
plied by suitable levers and actuates the re- 
cording pen which moves in proportion to the 
amount of mercury displaced. 

The time element of the meter consists of 
an eight day clock, which drives the drum 
feeding the paper. A paper Iced of one inch 
an hour has been adopted as standard and 
one roll of paper is sufficient for about a 
month's record. All recording meters are 
equipped with a re-roll device, which is oper- 
ated by spring mechanism, and is of sufficient 
capacity to accommodate one complete roll 
of paper. 

Compensating Devices for Pressure and 
Superheat Variation 

Tlic velocity of the steam being measured 
may remain practically constant, while the 
pressure and temperature vary over a con- 
siderable range; to obtain the actual rate of 
How in pounds per hour, it is necessary to 
compensate for the latter fluctuations. 

This compensation is made automatically 
in the ease of pressure variations, by a hollow 
spring, similar to the pressure spring in a 
steam gauge, which is connected so as to be 
influenced by the static pressure at the point 
where the How is being measured. Any 
variation of the static pressure causes I 
spring to expand or contract, and this move- 
ment act nates a small correction weight in 
such a manner as to affect the deflection ot 
the iien, so that the indicated rate of flow 
recorded by the pen is correct. 



A NEW TYPE OF METER 



137 



Compensation for temperature variation is 
made by an independent hand adjustment 
of the same correction weight that corrects 
the reading for pressure variations. This 
adjustment is made by increasing or decreas- 
ing the distance of the correction weight from 
its point of suspension; this distance is de- 
termined from a curve furnished with the 
meter. 



INDICATING FLOW METERS 

This type of flow meter will meet general 
commercial requirements where an indicating 
instrument is desired. It will be found 
especially useful for testing work, locating 
troubles due to leaks, etc. This indicating 
meter gives an accurate reading of instanta- 
neous rate of flow of steam or air or any other 




To A/ozz/e P/ug 



F/ex/b/e Stee/ Tad/rig 




Pressure Correct/or. 
Spr/'rg 



Bar/a/7c//?J> We/$/?t 

Pressure a/?d Te/7?p. 
Correct/on Weight 

C/ock 




Connecting 
Tude 



xs: 



Fig. 3. Recording Steam Meter 



Meters for Constant Temperature and Pressure 

In many stations steam is generated at 
practically constant pressure and tempera- 
ture; this will be found to be especially true 
where a battery of boilers is supplying 
to one unit. For such condition the .into 
matic pressure correction is not ei ntial, and 
the meter is adjusted by hand to suit the ex- 
isting conditions of pressureand ti mperature 



gas, at am condition of temperature, 
Mire. ,,r moisture. If used to measure 
ives a true indication of the in 

of How in pounds pei- hour per 
square inch of pipe cross sectional 

A ii is portable, a ingle meter may !><• 
utilized to obtain readings in any numb r oi 
different pipe line through a It is 

only necessary th be pro 



138 



GENERAL ELECTRIC REVIEW 



with the proper nozzle plug to which the meter 
can be connected. 

The meter consists of an iron casting which 
is cored out to form a U tube, which, as with 
the other types of meters, is filled for part of 
its height with mercury or water, and, as in 
their case, a difference of pressure in the nozzle 
plug causes a difference of level in the two 



*ck3 




Fig. 4. Indicating Steam Meter and Pipe Connections 

columns of the liquid. A small float sus- 
pended by a silk cord actuates a pulley over 
which the cord passes; the pulley, in turn, 
moving a small bar magnet on the end of shaft 
next to the dial in proportion to the change 
in level of working fluid in the U tube. 

The indicating needle is mounted in a 
separate cylindrical casing. Another bar 
magnet is mounted on the inner end of the 



needle shaft, and is free to turn in the same 
plane as the magnet on the inside of the meter. 
The mutual attraction of these two mag- 
nets keeps them always parallel, and by this 
arrangement the necessity of a packed joint 




Fig. 5. Indicating Steam Meter 

for transmitting the motion of the pulley to 
the indicating needle is eliminated. 

The pipe, receiver and nozzle plugs are of 
the same general design as those used with 
the recording meter. 

The proper adjustments for pipe diameter, 
temperature and pressure are readily made 
by setting the graduated cylinders which 
actuate the rack carrying the pointer. When 
these settings are made, the rack is rotated 
by hand until the pointer coincides with the 
indicating needle. The point on the gradu- 
ated scale at the intersection of the needle and 
pointer gives the true instantaneous rate of 
flow per square inch of pipe cross sectional 
area. 

Meters of both types have been in service 
in the Schenectady Works of the General 
Electric Company for several years, and their 
employment provides data for continuous 
records of steam and air used in the princi] al 
buildings, thereby indicating where avoidable 
losses may be eliminated. 

A number have been installed in this countrj 
and Europe, and have been giving satisfactory 
service under various conditions. 






TRANSMISSION LINE CALCULATIONS 

Part VI 

By Milton W Franklin 



L39 



LINE ECONOMICS 

The losses in a line are due only to resist- 
ance, but the line drop is a function of the 
line reactance as well as of the resistance so 
that the effective resistance must be con- 
sidered and not only the ohmic resistance. 

For a given voltage at the receiving end of 
the line and given power output at the 
generating end the most economical drop 
(resistance only) and power loss under 
certain conditions of cost of power, con- 
ductor, etc., may be mathematically com- 
puted. 

Let E R = Voltage at receiving station. 

P=Kw. output at generating station. 

L = Length of line in miles, length of a single 

conductor. 
c = Cost per kw. year at generating station 

in dollars. 
Ci = Dollars per lb. conductor. 
p — Interest rate on cost of conductors. 
Ai=Ohms per mil mile of conductor. 
A" 2 = Pounds per mil mile of conductor, 
A" = Total resistance of line (two wires) in 
ohms. 

5 = Cross-sectional area of conductor in 

circular mils. 
x = Loss in terms of generated power. 
Then line loss = Px (1) 

Annual cost of loss on line = cPx (2) 

Weight of conductors = 2LK 2 S (3) 

Cost of conductors =2ciKiLS (4) 

Interest per annum (conductors) = 2pciK 2 LS (5) 

2L 



Line resistance 

Line drop (At components only) = 

E R cos0x 1000 PR{\ -x) 
(l-x) ' ]-. R cos8 

Substituting value of A" from 6 we get 
E R cos8x = 2000 PKiL (1 -x) 
1 -.v 

C.S.A. of conductor =5 



(6) 



(7) 



E R cos8 S 
2000 (l-x)'PAiA 
E R cos 2 8x (8) 



The annual cost due to line loss and interest 
charges is then given by (2) + (5) =cPx+2pc,KiLS 

(9) 
The annual cost per generated kilowat' s the total 
annual cost divided by the generated kilowatts, = q 
_cPx+2pc i K i LS 
q ~ 1' (10) 



Substituting the value of 5 from (8) 

cPx + 2pc^L\ 2(m ^-^ rK ' L ] 
q= L E R COS*0x -I 

P 

Rearranging terms: 

_4000 pdKiKtLH 1 ,v)- 

E R Xcos-8x 
4000 pdKiKtL 



q = cx + - 



Putting K 



ex + 



cos 2 8 
A(l -*)» 



in (12) 



(11) 



(12) 



(13) 



Differentiating q with respect to x gives 



. dq 
Putting ~r ■■ 
& ax 



dx ,,. 



for the minimum value we get 



A 



In which A' 



cE R +K 

4000 pCjKiKvL 1 



(14) 
(15) 



(16) 



cos- 6 

and x = the most economic loss 

2000(l-xr-PA,A 
and 5= j 

E R cos 2 Bx 

Equations (14) (15) (16) are to be used for 
single-phase lines. 

If the preceding equations were worked out 
entirely with reference to the receiving end of 
line, the constants having the following 
significance : 

P R = kilowatts delivered (receiving end). 

x = loss in terms of delivered kw. 
E R = voltage at receiving end. 
cos 8 = power factor of load. 

Then we would have: 
K 



q = cx + 
dq 



K 



and (/v = c - 



= or 



A 



(17) 



(18) 



E R x' /-./. x 

which is the standard expression for interest = 
loss, a minimum for cost per delivered kw. 

With respect. tO line losses. 

In a three-phase (three-wire) system the 

area of each of the three wires is om 

the area of the wires used in tl m 

ing single-phase ease, so the weight of the 



140 



GENERAL ELECTRIC REVIEW 



metal is ■ three-fourths of that used for the 
same drop and loss. 

Substituting }K for A' in (10) will give fA 
instead of A" in (13). 



This gives x 



3 A 



1 4cE R +3K 



(19) 



The cross-sectional area of each conductor 
becomes 

1000(1 -x)"-PKJ. 

(20) 



5 = 



E R cos 2 8 x 



4000 pc,K,K<L- 
andA "= cos 2 e ^ before 



(21) 



Equations (19) (20) and (21) are to be used 
for a three-phase line when E R receiving 
voltage is given and, P, power generated is 
given, x being in terms of the quantities at the 
generating end. 



Single-Phase Line: E R receiving voltage known. 
P R kilowatts delivered. 
1 A~ 



S = 



= E R \c 
2000 P R K t L 

Ed X 



Id) 



W 



Three-Phase\Line: E R receiving voltage known. 
P kilowatts generated known. 



3A 



5 = 



N 4cEJ>+3A* 
1000(1 -xyPKtL 



(/) 



E R cos-6 x (g) 

Three-Phase Line: E R receiving voltage known. 
P R kilowatts delivered known. 

.866 ~K~ 
x= E~ R \c (A) 



Gm(\ 




Rece/w'na 
End 



Fig. 14 



The equations which apply in a three-phase 
system when we consider all quantities at the 
receiver end, are as follows: 

\__ JE .866 A 
X = E R \ c =£ fi \ (22) 



5 = 



1000 PrKxL 



1000 PK,L 



K = 



4000 pqKiKiL* 
cos'S 



(23) 



(24) 



ATsummary of the principal formul 
given Ix 'low: 

tOOO pctKi* 
K cos 1 6 (a) 

Single-Phase Line: E R receiving voltage known. 
P kilowatts generated known. 



-v 



A 



5 = 



cE R + K 
2000(1 -x)'P KiL 

E R cos*e x 



w 



(c) 



E R cos'0x («') 

Should the formula; on preceding page give 
a value of x which, when substituted in the 
equation for 5, gives a value of S which 
differs considerably from a standard sized 
cable, then x will have to be recomputed for 
the selected standard sized cable. 

The method is outlined below. 

Suppose S = computed size of cable with 
value .r, and we find the man st size standard 
cable to be. Si (circ. mils), it may be desirable 
to select this standard size cable S, and 
increase the loss of power slightly in preference 
to having a special cable drawn. 

Let A, be the resistance in ohms (single 
wire) of the cable S„ and let .ri represent the 
new loss corresponding to this case, then 



1000(J?.P) _ *i 
E R eos>e "0-") 2 



U) 



REGULATION OF THE PERCENTAGE OF CARBON DIOXIDE 



141 



. 1000(^,f) 

Let, z — — =a 

E R cos*d. 



<*) 



a can be easily calculated from our known 
values. 



Then, 1 =( 2j +"±^« + 1 



(0 



This formula for xi (the new loss) applies 
to single- and three-phase lines when the 
power P at generating end of line, E R receiver 
voltage, and cos e, power factor of load are 
given. 

Should the power Pr delivered to receiver, 
Er voltage at receiving end, and cos 0, power 
factor of receiving circuit, be given, then the 
new value of X\ is calculated from the follow- 
ing formula (formula applies to single- and 
three-phase lines) : 



E R cos- 8 



(m) 



Regulation of Line 

The regulation of a transmission line is 
defined as the percentage variation in voltage 
at receiver end between no load and rated 
non inductive load. 

In any but the shortest lines, the capacity 
may not be neglected, and various schemes 
have been proposed for calculating the 
capacity effect. 

The total line capacity may be regarded as 
concentrated and shunted across the line at 
the central point. 

This assumption introduces an error of 
about 1 per cent, in a 20(1 mile line. 

A closer approximation is obtained by 
regarding the total line capacity as divided 
into two equal parts, one of which is shunted 
across the line at either end. This method of 
approximation is sufficiently accurate for 
most praetieal eases. 

A still closer approximation is obtained by 
dividing the capacity into six equal parts and 
shunting one part across each end of the line 
and four parts across the center. This 
arrangement is illustrated in Fig. I I. 

The line inductance and resistance are 
regarded as connected in series with the line 
and divided as shown in the figure. X is the 
total line reactance in ohms, R equals line 
resistance in ohms, and C is the lin capacity 
in farads. 

(To '■■ I 



REGULATION OF THE PERCENT- 
AGE OF CARBON DIOXIDE 
IN FURNACE GASES 

Ry E. A. Barnes 



Much has been written and published in 
the last year or so on the subject of COs in its 
relation to boiler room practice, the writers 
having given much valuable information in 
explanation of COs, but little having been 
said of its praetieal application and the pit- 
falls attendant on its introduction into 
existing boiler rooms. 

In order to meet with even moderate 
success, the firemen who arc to do the work, 
as well as the engineer and superintendent of 
the plant, must be in harmony with the 
arrangement. It often happens that the 
introduction of CO2 economy methods in 
a power plant is turned over to a technically 
educated engineer who, through lack of 
practical experience, commences by calling 
for unnecessary refinements, especially with 
relation to sampling tubes in the boilers. 

He is also very insistent on taking samples 
from different passes in the boiler, and goes 
about the work as though the research and 
history of the CO2 percentage in the boiler 
itself was the thing to be arrived at; this, 
not being understood in the operating depart- 
ment, at once leads to complication and 
lack of co-operation. 

The primary object in introducing C0 2 
analysis in a boiler room is to save a percenl 
age of the fuel by scientific firing in place of 
the haphazard, unscientific firing that has 
been in use for so long. Tables prepared up 
to date show that this can be done, and tin- 
best way to accomplish the result is to have 
the simplest apparatus possible, and that 
which can be thoroughly understood and 
operated by the boiler room force. 

As firing under conditions that make for 
the greatest economy is much more un- 
comfortable for the fireman by reason of the 
greater amount of heal radiated from the 
boiler fronts, fire doors, etc., some form of 
extra compi osation, pre! rably in the form 
of a sliding scale premium system based on a 
fair allowance, mu t be worked out. 

In the opinion of the writer the 1 
to introduce the sampling tube is at about 
the center of the damper box or main flue 



142 



GENERAL ELECTRIC REVIEW 



breeching leading to the stack. This sampling 
tube should be of 1 in. or 1 in. common gas 
pipe, from three to six feet long, open at the 
ends and with a 1 8 in. slot through prac- 
tically its entire length. 

The pipe leading from the sampling tube 
to the rest of the apparatus need not be over 
1/8 in. standard pipe, securely and per- 
manently fastened to the boiler walls and 
equipped at the lower end with a suitable stop 
cock so that connection by means of a rub- 
ber hose can be made to the testing apparatus. 

A number of sampling devices have been 
designed, but the integrating bottle is the 
simplest, being nothing more than an in- 
verted bottle holding five gallons of water, and 
provided with a suitable drain and pinch 
cock so arranged that the flow of water from 
the bottle can be regulated to continue for 
.i certain predetermined period. The sub- 
siding of the water forms a partial vacuum 
and_ sucks in the products of combustion 
from the sampling tubes in the boiler. This 
bottle is removed periodically and gases 
therein tested with the regular Orsat ap- 
paratus, the average C0 2 percentage through 
this period being thus arrived at. 

There is another instrument called the 
econometer, in which the weight of flue gas 
as compared with that of the atmospheric 
air is constantly indicated on a scale. 

The inverted hell sampler, as its name 
indicates, is a glass bell inverted in a water- 
sealed glass chamber. This is designed to 
operate by clock work and is suitably 
balanced. The rate at which the bell is 
withdrawn from the water-sealed chamber 
ids, of course, on the adjustment of the 
clock and the duration of time over which 
tin' samples arc to be taken. 

There is also the automatic motor-driven 
1 >i a1 with recording adjustments, of which 
there are several designs on the market. 

All the latter automatic instruments re- 
quire a great deal of supervision, and 
unless kept in thorough working order, 
their indications cannot In- depended on. 
As before stated, the simplest form of ap- 
als most strongly to the average 
plant. Various conditions of induced draft, 
forced draft, natural draft, automatic sto 
hand firing, etc., etc., all introduce factors 
that tend to change the results and call for 
different handling in different installations. 
In this article, we will O -inly hand 

fired boilers having induced draft. 

In a hypothetical case, we will assume that 
the COj averages about 1 1 or 1 2 per cent., and 



things go along very nicely for months, when 
all at once it is called to our attention that 
certain boilers are not holding up their 
percentage. Investigation is made, and it is 
found that the fireman has the dampers shut 
down and everything apparently in good 
condition. The boiler brick work is examined 
and it is discovered that there are innumerable 
cracks in the brick work around the clean- 
out doors and on top of the boiler where the 
domes and drums protrude. As soon as these 
are cemented up with suitable cement the 
C0 2 percentage at once goes back to the 
normal condition. It is the excess of air 
entering in through these leaks that has 
caused the trouble. Without the tell-tale 
C0 2 percentage showing, this waste would go 
on unchecked indefinitely. 

Where a number of boilers in the same 
plant are being fired by men on a premium 
system, it is necessary to have some form of 
counting apparatus for each boiler or set of 
boilers handled by individual firemen. If 
this is not done, the wise firemen will keep 
their dampers closed and burn a very light 
fire and get a high percentage of C0 2 during 
the shift, but will consume little coal. The 
other fellows, who are shoveling in con- 
tinuously, have their doors open and not 
only their C0 2 percentage goes down, but 
they are doing all the work and not getting 
as much pay as the men who are holding 
back. The counters are intended to indicate 
the amount of fuel fired per man. 

Another point that is well to bear in 
mind is that the boiler settings as specified 
by the boiler makers in many cases are not 
properly worked out for the excessive luai 
that has to be withstood inside of the fire box 
and boiler settings under the new conditions. 
It has been my experience that nothing but 
the highest grade of lire brick should be used, 
and that the fire box lining brick should be 
laid up in courses of two stretchers and one 
header alternately. It is also very desirable 
to have every fourth header brick specially 
long, say IS in., so that it not only binds the 
inner skin of high grade brick, but hangs over 
and is toothed into the low grade brick that 
usually constituted the intermediate filling. 

If these precautions are not taken the 
excessive heat will warp and burn away the 
inner lining, causing it to bulge and crack, 
and there is danger of letting down the main 
arch. These precautions may seem unneces- 
sary, but if results are wanted they must be 
carried out. 



PAY-AS-YOU-ENTER CARS 



l 13 



With regard to the arches, they must also 
be built of the highest grade brick, and 
should be laid out in the drafting room full 
size — so many straight brick and so many 
wedge brick — so that the masons who do the 
work will lay them up in this way. If this 
is not done, the arch will fail because the 
masons will use straight brick clipped into 
position and fill in the top crown with a lot 
of spalls and fire clay mortar. 

I have mentioned above that different 
plants require different treatment, and I 
know of one - plant in particular in which 
chain grates are used, where the clearance 
allowed around the chains and back of the 
chains is so great, that enormous quantities of 



excess air enter at these points, and a low 
percentage of C0 2 results. 

Where chain grates and automatic stokers 
are employed all clearances must be cut down 
so as to reduce to the lowest possible per- 
centage the amount of air that does not pass 
through the fuel bed. 

Among other important things that should 
be found in an up-to-date fire room are 
colored glasses through which the fireman can 
examine their fires. It is only by firing often 
and light, and covering over the "rat holes" 
and preventing the ingress of excess air that 
the best results can be attained. It is also 
very necessary that the draft be cut down as 
.nuch as possible. 



THE PAY-AS-YOU-ENTER CARS ARE TIP-TOP 



m "Life") 

Mr. Whitridge said he thought so much of the pay- 
as-you-enter cars that he hud bought S76 of them since 
the type was tried on the first Third Avenue system. — 
Daily paper. 

They are admirable; vastly better than the old 
style cars for the people who ride in them, as well 
as for the corporations that furnish them. They 
catch all the fares, which is right. They do away 
with constant progresses of the conductor through 
crowded cars, which is a great relief. They make 
for order, sense and better manners. They do away 
with the nuisance of smokers on the platforms and 
give the companies a better chance to exclude 
lighted cigars and cigarettes from the ears alto- 
gether. Publish it to the world that rides in street 
ear< that the pay-as-you-enter cars are a great boon 
to mankind, and a remarkable mitigation (it the 
sufferings of city population: . 



The pay-as-you-enter cars have found favor 

with the street railway corporations of the 
larger cities and with the public, and since 
their introduction on the Third Avenue sys- 
tem, New York City, about two years ago, 
they have been put in operation on the more 
congested thoroughfares of Chicago, Balti- 
more and Detroit. It is also very likely that 
other large cities in the country will adopt 
these cars in the near future. 

The logical arrangement of se] doors 

mii entrance and exit, and in some cases the 
i mployment of the rear and front platforms 
respect ively for these purposes, goes far 
towards eliminating the delay ps due 

to interferi to b I 'ecu per ons boarding and 
leaving cars of tin- ordinary enclosed type. 
Tlie annoyance spared the passenger by this 




Convertible Pay-as-you-enter Car for New York City 
Arranged for Winter Service 



144 



GENERAL ELECTRIC REVIEW 



single feature does much to commend the 
pay-as-you-enter car to his favor and thus 
win his fare. 

Accidents are also largely prevented by the 
fact that the conductor is stationed at the 




Conductor's Platform, Convertible Pay-as-you-enter Car 



rear platform, in a position to render assist- 
ance to wonnn and children boarding the 
car, to the crippled, and to these otherwise 
incommoded. He can also see at a glance 
whether his platform is clear, and can signal 
his motorman without delay and without 
danger of injury to his passengers. 

The illustrations show one of the 300 
pay-as-you-enter ears furnished the Third 
Avenue Railroad bj the J. G. Brill Com- 
pany last summer. This ear is an adapta- 
tion of the Brill patented convertible car, 
and is the result of an effort to embody the 
prepayment idea with the open ear arrange- 
ment. Fifty additional ears of almost iden- 
tical design are now tin order for the same 
System. These ears will he fitted with 
GE 210 volt, 7(1 h.p. motors. 



OBITUARY 

Mr. H. H. Buddy, Manager of the Power 
and Mining and Lighting Departments of 
the Philadelphia District of the General Elec- 
tric Company, died on the morning of Jan- 
uary 15th after an illness of but two days, 
his sudden death coming as a great shock to 
his many friends. 

In Ins."). Mr. Buddy, who was then about 
1 7 years of age, entered the employ of the 
Accounting Department of the Thomson- 
Houston Electric Light Company, of Phila- 
delphia, and he was later promoted to the 
Commercial Department of that company. 
Upon the organization of the General Elec- 
tric Company, he was made the Manager of 
the Power and Mining and Lighting Depart- 
ments of the Philadelphia District, which 
position he filled with marked ability anil 
continued to occupy until the time of his death. 

Throughout his business relations he secured 
and maintained the respect, confidence, and 
friendship of many of the prominent men 
connected with the large corporations in that 
territory, and the grief at his death was wide- 
spread. 

Mr. Buddy was a member of the Meriorj 
Cricket Club of Haverford, the Art Club of 
Philadelphia, the National Electric Light 
Association, and an Associate Member of tin- 
American Institute of Electrical Engineers. 

The funeral services were held at the house 
of a friend on Mt. Vernon Street. Philadel- 
phia, and the interment was made at Haddon- 
field. New Jersey, where his wife and child 
were interred about 15 years ago. He is 
survived by a father, a sister and a brother. 



BOOK REVIEW 

THE THEORY OF ELECTRIC CABLES 

AND NETWORKS 

By Alexander Russel, A.M. D.S.C. 

D. Van Nostrand Co. 269 Pages Price $3.00 Net 

This 1 k appi udents and to managers of 

the smaller central stations who are contemplating 
some underground installations. It is written from 
the English viewpoint and refers almost entirely 
to English and Continental methods of cable con- 
struction anil installation. 

I hi most valuable chapter in the book is that 
Mealing with the dielectric strength. This anil 
following chapter on tin- "Grading of Cable" make 
clear the undesirability of using very small cond 
t"rs for high potential work. 

The references at the ends of the chapters are 
decidedly the best things in the book, since the some- 
what scanty literature on the subject of cable 

ttered through numerous publications in papers 
by various authors covering one or more branches 
of the subject. 




VOL. XIII, NO. 4 



Cc 
by General EUctric Comp 



APRIL, 1910 



CONTENTS 



Editorial .... 

The Westport-Stockton Coal Company's Colliery, Westport, New Zealand 

By W. A. Ri i i i 



147 
1411 



Commercial Electrical Testing, Pari VI 

Bv E. P. Collins 



15!) 



Electricity on the Farm 



By John LlSTON 



Hyperbolic Functions and Their Application t" Transmission Line Problems, Part I 

By W. E. Miller 



166 



The Elements of Transformer Co ion 

By W. A. 11 \n 



181 



Key for the Complete Calculation of a Transmission Line 

\\\ M. W. Franklin 



186 



entation < if Edi < >n Medal 



191 







' 



ELIHU THOMSON 




TRANSMISSION LINE PROBLEMS. 

If collected, the literature dealing with 
Qsmission line problems would fill many 
volumes, and the subject has been treated 
from various points of view. As it lends it- 
self readily to theoretical treatment, the 
question has been discussed mathematically 
to a greater extent perhaps than any other 
branch of electrical engineering. 

In the February number of the Review, 
Mr. M. W. Franklin shows how to derive 
the exact solution of the problem by means of 
the hyperbolic functions. The equations 
so obtained involve certain constants which 
include the geometrical properties of trans- 
mission lines, i.e., their self induction and 
capacity, as well as the resistance and fre- 
quency, and necessitate the evaluation of the 
constants and of the hyperbolic functions 
before numerical results can be obtained from 
them. 

The articles, by Mr. W. E. .Miller, com- 
mencing in this issue, are of value because 
these constants, as well as the hyperbolic 
functions, have been computed at sufficiently 
close intervals to allow of ready and accurate 
interpolation by inspection, for all values of 
the constants and functions which lie within 
their range. Tables of these functions will 
be published in a supplement to the next 
issue of the Review, which will contain the 
transmission line equations and examples 
showing how to use them. By the aid of the 
tables, numerical results can be immediatelj 
obtained from the equations by multiplii 
tions <>f two, oral mosl three complex quanl i 
ties, ainl two simple divisions. No capacity, 
self induction or resistance need he found, 
ause these are included in tin COl 

As the wires in transmissi m lines are very 
often strung equally spaced with their axes 
lying in a plane, as well as at the corners of an 
equilateral triangle, the con tants have been 
calculated for both methoi 

The great advai 
solution of the problem is that the electri 



conditions can be as readily determined at any 
point of the line as at the generator or re- 
ceiving end, so that if a branch line is con- 
nected at any point, the electrical characteris- 
tics at its junction with the main line can 
be immediately obtained. 

Apart from this practical aspect of the ca 
it is of some educational value to ee how the 
\olts, amperes and power-factor vary along 
lines of great length, for which approximate 
solutions are not reliable. The length at 
which most approximate met hods fail can 
be roughly taken as 200 miles at 60 cycles, 
and 400 miles at 25 cycles. The complex 
hyperbolic functions in these articles have 
been calculated to take care of lines up to 135 
miles in length at 60 cycles, and 850 miles at 
25 cycles, even when using the smallest wire 
considered. Slightly longer lines can be 
calculated, when larger wires arc employed, 
though the difference is immaterial. 

The knowledge of the hyperbolic functions 
and of the complex quantity possessed bj 
the majority of engineers, is small, and for 
this reason a short discussion has been given 
of these matters, which should prove useful 
to-those who wish lo get some insight into 
these quantities. Their understanding is 
important if the meaning of the equations and 
their operation are lo be understood. The 
analog}' is traced between the circular and 
hyperbolic functions, and there can be but 
little doubt that if the hyperbolic functions 
were taught in school or college in conjum 
with plane trigonometry, very little extra 
work would be required for appreciating and 
handling them. 

In following is-ii* Review, curves 

will be given illustrating how the 
characteristics vary alo ansmission line 

loo miles in length at ■ ■ '•• ;, with va 

inal i onditions at the receiving end. 

A considerable amount of interest is now- 
being taken in coi and th< n 
this question is briefly considered, curves 
being drawn in which the corona loss is 



1 is 



GENERAL ELECTRIC REVIEW" 



separated from the capacity current loss along 
the line at no load, the example taken being a 
200 mile line using No. 1 wire and operating 
at 25 cycles. 

Amongst other points discussed, the follow- 
ing may be mentioned: transmission ef- 
ficiency, velocity of power propagation, 
shift of phase, and variation of power-factor 
along the line, a method being given for 
discovering under what conditions maximum 
transmission efficiency can be obtained for a 
given load at the receiving end. As an in- 
teresting case in the use of hyperbolics, the 
volts and amperes of a 1000 mile telephone 
line have been calculated at various points 
of the line, both the maximum and instant- 
aneous values of these quantities being plotted. 
A short discussion on a few of the theoretical 
points in connection with telephone lines 
rinses the articles. 

The table of the hyperbolic complexes and 
the constants required for transmission lines 
been calculated with the greatest pos- 
sible care, and, through the greater part of 
the range, the accuracy is about one-quarter 
per cent. Greater accuracy is not attempted, 
not only because it is not generally required 
in electrical engineering, but also because the 
labor involved would have been enormously 
increased, since a slide rule could not have 
been used. It is hoped that few errors occur 
in the tables, but in work involving over twevle 
thousand separate calculations, it is practical- 
ly impossible to entirely avoid mistakes. 
There is little doubt, however, that no serious 
discrepancies can exist. 

ELECTRICITY ON THE FARM 

Tip' high ami ever increasing cost of living, 
which, it is well recognized, is due in a \<t\ 
measure to the scarcity and the COD 
sequent steady advance in the cost of farm 
produo i usiiio the necessity for greater 
production to assume vital economic im- 
portance. 

The nci d [cultural a immodities 

is urgent, ami the reward for i he producer 
certain, but the problems involved are many 
and perplexinj chiei one being thai of 

lecuring efficieri labor al a rational, or in 
n . . price. This difficulty may be over- 
come to an extenl m i1 ly realized by 
i hi' utilization of < Eor reducing the 
manual lab a nece ary. In pursuant 
this ci iur e, man} mi idem farms have 
equipped with labor saving machinery and, 
this solution has been applied to tin- 



problem, the results have far exceeded the 
expectations and have more than justified 
the investment; not only by greatly increas- 
ing the output, but by doing away with "the 
discouraging and never ending hard work 
which in the past has done more than any 
other thing to drive the boys from the farm." 

In the great grain districts of the North- 
west, agricultural operations have, of course, 
long been accomplished by the use of ma- 
chinery; the harvesting, etc., of these enor- 
mous crops would otherwise be an utter im- 
possibility. In Europe also, and especially 
in Germany, plowing and similar operations 
have been performed by means of electrically 
driven machinery. These methods have re- 
sulted in material economies, and this al- 
though the land is poorer than that in the 
United States and the cost of labor only 
about one-sixth of that in this country. 

While in the Eastern states, the employ- 
ment of engine or motor driven machines 
for the more extensive operations may not 
fit the present conditions, the uses for power 
on an average American farm are many and 
varied. The threshing and grinding of grain, 
the operation of separators, churns, and pumps 
(both for regular water supply and for service 
in case of fire), the driving of washing ma- 
chines and other household devices, are only 
a few of the labor saving items. 

For the purpose of driving farm machinery, 
the electric motor is ; he logical choice; there. 
if anywhere, it stands pre-eminent. The 
flexibility of the electric system; the fact 
that a number of scattered motors used for 
intermittent service may be supplied from a 
small generator of very much less than the 
aggregate capacity of the motors; the 
availability of the current for lighting pur- 
poses and the absolute safety as regards fire 
risks; are but a few, and not necessarily the 
most important reasons for the selection of 
electricity as the motive power. The further 
i. id thai with the introduction of electricity 
conic many material comforts, and even 
luxuries, is another cogenl reason for its 
adoption; and when in addition to the above, 
it is realized that the power for generating the 
current can. in very many cases, be obtained 
from local streams, the energy of which would 
otherwise be wasted, the superiority of elec- 
tric j lower becomes evident . 

The article by Mr. Liston, in the pn 
issue, describes a large model farm in which 
icity has been utilized extensively and 
found reliable, safe, and 

lomical. 



149 



THE WESTPORT-STOCKTON COAL COMPANY'S COLLIERY 
WESTPORT, NEW ZEALAND 

By W. A. Ref.cf. 



With the opening of the Westport-Stockton 
Coal Company's Colliery on October 6th, 
1908, an engineering work was successfully 
brought to completion which 
affords not only a striking 
example of a modern coal 
mine equipment in its highest 
perfection, but also offers a 
most interesting study of how 
a difficult and complicated 
haulage problem was over- 
come, involving as it did, the 
introduction of electric hoists, 
gravity inclines, and electric 
locomotives. 

k In order to give an intel- 
ligent idea of the work, it 
will perhaps be best to first 
describe the coal formation, 
taking up the various other 
considerations such as power 
plant equipment, haulage 
systems, transmission . line, 
braking problem, etc., in 
order. 

The Company holds a Crown lease of two 
thousand acres of coal bearing land forming 
part of the Buller coalfield. From the out- 
croppings and test bores the famous Westport 
seam of coal — a bituminous coal of high 
calorific power and great purity- was proved 
to underlie the greater part of the 2000 acre 
area. The scam is from eight to twenty feet 
in thickness and has a fine roof of hard sand- 
stone and in most places a hard bottom of the 
same material. The lease is situated on the 
tableland of the steep coastal range, a1 an 
elevation of about 2000 feet above sea Level. 

The Buller coalfield may be described as 
unique. The coal lies at a moderate incli- 
nation on the coastal range plateau, and is 
underlain by sandstones which repose directly 
on granite. The thickness of these sandstones 
rarely exceed LOO ft. and in some portions of 
the field the granite intrudes into the coal. 
The coal formation belongs to the Cretacio- 
Tertiary, bu1 the coal is truly bituminous in 
compo ition ind characteristics. Gold is found 
in the immediate vicinil y of the coal mea lure >. 

Power Considerations 

The coal is brought down In. I the Com- 
pany's mines to tin Go ernment railway at. 



Ngakawau, which is 19 miles from Westport, 
the port of shipment. The distance from the 
Company's tipple at Ngakawau to the siding 




Power Station with Tipple and Bins in the Rear 

in the mine, from which the coal is hauled by 
the Company's main haulage system, is four 
miles. It was decided to install electric power 
for the whole of the mining operations and to 
generate it in a central station at Ngakawau; 
the reasons for locating the plant at this point 
alongside the government railway being as 
follows: 



augmenting the 
available water 



t L) Possibility of later 
steam power by 
power. 

(2) Saving of difficult transportation and 

the facilii te i offi red bj I he Ngakawau 
site for economical handling and 
erection. 

(3) Proximity to tipple, facilitating the use 

of creenings from the coal for power 
plant fuel. 

(4) Besl Location for supervision. 

Power House 

The power-house is of 6 
struction and is SreprooJ throu [houl 
I7t ft. long by ■"><> ft . wide, and is divided into 

thro D • mpartmeii 
room, and boiler room. 

There are tv i each 

consi 300 Lev . 6600 roll . 60 



1 .-,1 1 



GENERAL ELECTRIC REVIEW 



three-phase generator direct connected to 
and resting on a common bedplate with a 
A7~> b.h.p. Bellis & Moreom triple expansion 
engine, the set running at 400 revolutions 
per minute. 

In addition there are two exciter sets, each 
made up of a 1-1 kw., 88 volt, 600 r.p.m. 
generator direct connected to and on a 
common bedplate with a Bellis & Moreom 
single expansion engine run condensing. 
For lighting about the planl and for operating 
a number of 'I.e. motors on the conveyors and 
jiggers in the main coal storage Litis, a mol >r- 



Two blank panels. 

Two main generator panels. 

Main high tension feeder panel. 

Blank panel. 

Two exciter panels. 

The direct current voltmeter for the 
motor-generator set is mounted on the 
extreme left panel, the synchronizing indi- 
cator and exciter voltmeter, together with 
voltage regulator, being mounted on the 
extreme right panel. 

The engines exhaust into a Worthington 
surface condenser, which has a capacity of 




Generator Units in Power Station 



generator set is installed in the power-house. 
This set consists of a loo kw., 280 volt flat 
Compound direct current generator direct 
ected to a 150 h.y 6300 volt, form K, 
phase motor, the set running at 70.") 
r.p.m. 

The main switchboard comprises eight 
panels of blue Vermont marble and three 
blank panels to provide for future extensions. 
From left to right the switchboard is made 
up as follows: 

Feeder panel for or of motor-gener- 

ator set. 

Generator panel of motor-generator 

Starting panel for motor of motor-generator 



30,000 lbs. of steam per hour with the cir- 
culating water at a temperature of 55 deg. F. 
A Worthington centrifugal pump draws 
circulating water from a well near the power 
house. The air pump, which is of the three- 
throw "Edwards'" type, is driven by an 
engine of 25 b.h.p. condensing. A Webster 
feed water healer which is capable of raising 
the temperature of .'III. noil lbs. of water HO 
F. in one hour, is installed and uses the 
exhaust steam from the two boiler feed pumps 
and the engine driving the automatic stokers. 
There are four Babeock & Willcox boilers, 
each with a heating surface of 1690 sq. ft. and 
a tire grate area of .'! 1 sq. ft. and capable of 
evaporating 5000 lbs. of water per hour at 



THE WESTPORT-STOCKTON COAL COMPANY'S COLLLIERY 



151 



212 deg. F. The boilers are fitted with 
Babcock .superheaters which superheat the 
steam 150 deg. F.. and with automatic stokers 
of the Babcock chain .urate type havinj 
speed feed gears and driven by a 1") b.h.p. 
single engine. 

The boiler feed pumps, of 
which there arc two, arc of 
"Tangye's" manufacture and 
have each a capacity of 75,000 
lbs. of water per hour against 
a pressure of 150 lbs. It will 
be noted that the condenser 
plant and the feed pumps 
are of sufficient capacity to 
take care of the u 1 1 i mat c 
engine and boiler capacity of 
the plant, which will be double 
that at present installed. 

Hoists 

Two small auxiliary panels 
are located near the main 
switchboard in the power 
house, one of which is em- 
ployed for the control of a 4(1 
kw., 6600 230 volt transfor- 
mer. This transformer sup- 
plies current to a ~>2 b.h.p. 
motor connected to a Lidger- 
wood hoist located near the 
bins, the hoist being used for hauling t he govern - 
ment railway coal trucks out of a dip onto 
an incline. From this incline the trucks are 
distributed by gravity to the various tracks 
under the bins for loading; after which they 
arc run by gravity to the main siding and 
there made up for dispatch to Westport 
harbour. The second auxiliary panel is for 
the control of a 75 kw., 6600 230 voll trans- 
former supplying current to a ! 1 '_' b.h.p. 
motor connected to a second Lidgerwood 
hoist. This hoist has two drums with 
main and tail ropes and brake and friction 
clutch levers, and is used for hauling tin- 
loaded coal tubs from the fool of the lower 
incline through the Ngakawau tunnel to the 
bins, and for returning the empties: the 
method of haulage being main and tail rope 
A' auxiliary ai ml i ;il provided 

so that tubs, stores and miscellaneous ma- 
terial can 1>" hauled up from the shops and 
o i lie tunnel moul h. 

Haulage Way 

Ngakawau tunnel. The Ngakawau tunnel 
is 2s chains long with an avi I dient oi 

1 in 60 in favour of the load. The tunnel 



commences about 100 yards from the bins 
and runs through to the foot of No. I incline, 
a single track of III lb. per yard rails being 
laid, with sidings at each end. 'The method 
of haulage, as previously mentioned, is by 
main and tail rope, and the tubs can be run 




Switchboard : n Power Station 

in sets of 2.") at the rate of four round trips, or 
inn t ubs per hour. 

Gravity Inclines 

The lower incline is 33 chains in length and 
lias an average gradient of 1 in I and a 
maximum gradient of 1 in ■'!. At the top of 
this incline is located a Hat where the mine 
tubs are changed from the upper incline rope 
io i hat of the lower incline. The upper 
incline is 1(1 chains in length with an average 
gradient of I in 6.7 and a maximum gradient 
of 1 in 5. These inclines have been most 
careful];, graded; there arc no dishes, ami 
changes of gradient have been effected by 
sin- vertical curves. Towards the bottom of 
the upper incline there is a sandstone tunnel 

i chains in length, but on the lower 
incline there are no tunnels. Heavy cuttings 
and fillings have had to be constructed on 
both ■ icing, been resorted to 

where ira dging, 

with a vii "i main- 

tenan 

A double trai k of 40 lb 
of ill,- , inclim and are operated 

by gravity, the endle tulage 



L52 



GENERAL ELECTRIC REVIEW 



being used. The tubs are spaced on both the 
full and empty sides at intervals of 1§ chains, 
the greater weight on the loaded side causing 
the motion. The speed of the rope is regu- 
lated by powerful four-cylinder hydraulic 
brakes of the vertical type, which were built 
by Messrs. Simpson Brothers, of Sidney, 




Hydraulic Brakes for Gravity Incline 

alia. The braking is i ! by churn- 

ing the water from end to end of the cylinders 
through by-pass valves, a small quant c 
water being admitted and a small quantity 
expel! h stroke to keep the water cool, 

e brakes act admirably, imparting a 
motion to the ropes and giving good 
speed regulation. 

Verl oved pulleys in ft. in diameter 

are employed in place of surging drums to 
eliminate side friction between the coils of 
braking pulley lias five grooves 
turned to lit tli.- ropes, and the idler pullej 
four-. The incline ropes are of Shaw's 

manufacture and are made of the best patent 
plough steel wire, the lower incline rope 

I '. in. in circumference and the u 
incline rope I in. 

Tin' mine tubs are built of mild steel with 
n buffers and 12 in. diameter casl 
fast wheels of Hadfield's make set for '.I ft. 
The tubs weight 1- cwt. empty and 
have a carrying capacil and when 

spaeed every \] chains and travelling two 
miles per hour, have a capacit} : lOtons 



per hour. With the tubs spaced every chain 
and travelling at the same speed, their 
capacity is increased to 240 tons per hour. 
The rope runs under the tubs and is attached 
to each by means of chain clips. The tub 
drawbar is provided with a hook, and the 
clip chain, which is made with a large link at 
each end, is wound three times 
round the rope, one end being 
then passed through the other 
and hung onto the tub 
hook. The lower incline clips 
m ^_^^^^^ are made of f in. diameter 
Staffordshire short link chain 
and the upper incline clips of 
similar chain 5 in. diameter. 
These clips hold well on the 
steep gradients, and so far 
not the slightest trouble with 
them nor with the hydraulic 
brakes has been experienced. 
It is surprising with what 
facility boys can handle these 
clips. Before employing the 
chain clip, a patent screw 
clip was tried, in which the 
rope was held in a sort of vise; 
but it was found that with 
this clip the personal factor 
came too much into play, 
and one clip insufficiently 
screwed up might be re- 
sponsible for a serious wreck. 
An accident of this kind actually happened 
on one occasion when a loaded tub got away 
on the lower incline on the 1 in .'> grade and 
cleared the rope of all tubs below it, piling up 
and wrecking about 14 tubs. 

Electric Haulage System 

Ai the head of the upper incline, which is 
termed the brakehead, the trucks run onto a 
level plat where the main electric locomotives 
mi their run. These locomotives deliver 
the loaded tubs from the mini head of 

the upper incline and pull back the empties. 
At present the Company has three of these 
main locomotives (an additional one being on 
order) and two gathering locomotives. The 
main locomotives weigh 20 tons each and 
equipped with Sprague General Electric Type 
M control to permit them to be worked as 
separate units or coupled in tandem as 
required. Each locomotive has a drawbar 
pull of 7">00 lbs. and a sped of 8.2 miles • 
hour. The length of the tramway from the 
brakehead to the mouth of "A" tunnel is 2', 



THE WESTPORT-STOCKTON COAL COMPANY'S COLLIERY 



153 



miles, and from the latter point the track runs 
for half a mile in the mine through a coal 
tunnel 8 ft. high and 7 ft. wide to the layby, 
where the loads are at pre- 
sent picked up. 



Braking Problem 

The vertical rise in this 2\ 
miles of track is 71 feet, giv- 
ing a gradient of 1 in 20.5. 
There are several curves en 
the track and the minimum 
radius is two chains. Up to 
the present time the locomo- 
tives haw been used singly, 
nn difficulty having been 
experienced in hauling the 
empty tubs up to the mine. 
The train is made up of 
twenty empties weighing 12 
cwt. (112 lbs. per cwt.) each, 
and a braking ear weighing 
two tons; making a total 
train load on the up grade 
of] I tons. Braking the loads 
down has proved a much 
more difficult problem. In 
the first place the center rail for the Fell 
brake was laid only on the steeper gradients 
and the tubs were all fitted with wheel brakes 



for the first half mile of the run as there 
was insufficient room in the tunnels for a 
man to get from tub to tub: and even outside 





Train of Cars Leaving Tunnel 



independent^ operated. These brakes were 

el before the train started from the mine 

and it was impossible to manipulate them 



Fell Center Rail Brake 



it was not practicable to work the brakes 
in this way owing to the small clearano 
between line and trolley poles which made 
it dangerous for the brakeman to pass over 
the tubs. 

The result was thai the brakes were 
often set so tight as to skid the wheels, 
or else so light that there was verj little 
braking effected. It was early discovered 
that the locomotive wine] brake in con 
junction with the tub brakes could not 
be relied upon for braking the train, even 
on the flattest grades, and it was nei i 
to put in the center rail from end to end 
of the track. It was also found that 
accidents occurred at points where th 
ter rail had to be picked up by the 
called Fell center rail grip brake, owing 
to the fad that the brake occa ionally 
struck the end of the rail. After m [tailing 
tlie center rail throughout the entire liaul- 
di I ,'inee, it w.i found t hat 

brake, tlthough powerful ■ o control 

the speed of tlie train with the 
of the tub brakes and wheel brake, could 
not be depended upon to stand the I 
ing and strain of continuous runnii 
The loaded tubs weigh il' cwl . each ami 

the v ' i in load i S thl 



154 



GENERAL ELECTRIC REVIEW 



tons plus the 20 tons weight of the locomotive, 
or 62 tons. On the Rimutaka incline of the 
New Zealand Government railway, the train 




Gravity Incline 



carded on account of the difficulty of effect- 
ively manipulating them and the heavy cost 
of upkeep. On the up-trip to the mine with 
the empty tubs, the braking car is 
placed at the rear end of the train 
and is run with the Fell brake down 
ready for action should a coupling 
break. On the downward trip, how- 
ever, better results are obtained by 
running the car at the front end of 
the train next to the locomotive, as 
in this position the brakeman is more 
in touch with the driver and can 
apply the brakes as required. 

In making the down trip with the 
braking car at the rear end of the 
train, it was found that on approach- 
ing a brow the car brakes were 
sometimes applied too soon, thus 
throwing a severe strain on the 
couplings, or else not soon enough, 
throwing the whole weight on the 
locomotive. It is believed that it 
would not lie advisable to run the 
locomotives in tandem, owing to the 
excessive amount of current that 
would be required in ascending 
steep grades on the up-trip and to 
the severe strain the buffers would 
be subjected to on the down-trip 
unless two braking cars were em- 



load allowed per Fell brake on a 1 
in 1 l grade is 20 tons. On one 
occasion, after tin- equipment had 
been in operation a few weeks, the 

Fell brake gear earned away on a 
downward trip, fortunately at such 
a poinl thai the damage caused was 
not great and the driver escaped 
injury. Should such an accidenl 
occur near the top of am- of the 

,n- 
ration, which, by the way, is the 
most likely pla m accidenl of 

the kmd io occur, it would probably 
wreck thi' locomotive and train and 
kill the driver. Ii was therefore 
decided to add a braking ear fitted 
witli a second Pell brake, to be used 
in conjunction with the locomotive 
Fell brake ami jufficientlj powerful 
to brake tin- whole train load in 
ease of emergency; the most i< 
proved braking car being lined with two 
Fell brakes. This method has proved 
factory and the tub brak n dis- 




Motor-Generator in Substation 



d, one next to the locomotive as at 

■ i'. and one at the rear end of the 
train. 



THE WESTPORT-STOCKTON COAL COMPANY'S COLLIERY 



The wear and tear on brake shoes is very 
heavy, the wheel brake shoes lasting for only 
eight hours and making about eight trips. 
I; was found necessary to design the Fell 
brake shoes with removable wearing strips, 
mild steel proving must economical for the 
purpose and giving the besl results. Cast 
iron was found to wear away very quickly 
and consequently required to be heavier and 
was considerably more costly. A set of 
mild steel wearing strips lasts about eight 
hours, as stated above. 

The smaller gathering locomotives weigh 
rd, tons each and have a drawbar pull of 
2500 pounds and a speed of 7.4 miles per hour. 
These locomotives are used for the subsidiary 
haulage from the working places in the mine to 
the siding from which the main haulage starts. 
They are equipped with a reel which is 
mechanically worked from the locomotive axle 
and which is supplied with 900 feet of flex- 
ible twin cable, thus permitting the locomo- 
tive a considerable range of operation beyond 
the point of overhead construction. 

Track 

The track from the brakehead into the 
mine is 36 in. gauge and of extremely solid 
construction. The rails are 40 feet long and 
weigh 56 lbs. per yard; they are laid on 8 in. 
by .") in. ties and are bonded at each joint 
with two number 00 bonds and cross bonded 
at every third rail. The distance from the 
brakehead, where 'he main locomotives 
deliver the loaded trains to be conveyed by 
gravity down the endless rope inclines and 
thence through the Xgakawau tunnel to tin- 
bins at No. 1 substation, is .'!."> chains, with 
a minimum curve of L 32 ft. radius and the 
grades varying from 1 in 32 to 1 in 12, or an 
average of 1 in 25, all in favour <>( the load. 

From Xo. I substation to No. 2 subst; 

at the mouth of A tunnel is 1 4."> chains, tin 

grades all being in favor 7 the load and 

varying from 1 in 12 to level, the average being 

1 in 21 . The minimum radius of curves is 

L32 ft. From Xo. 1' substation to Xo. :i 

•station, through A ami P. tunnels, is 79 

lins, the A tunnel being 1 '< chains long and 

B tunnel HI chains long. The distance 

iy, where the coal is at present 

lifted, is in chain . the track being traight 

and the minimum grade I in 12. 

Overhead Construction 

The trolley wire i- 7 ft. 8 in. above the level 

of the head of the rails, and t of Xo. 0000 



throughout. In parallel with the trolley for 
the whole run is a bare stranded cable of 
600,000 cm., the latter being tied to the 
former at an average of every 150 feel 

Sub-Stations 

Three sub-stations, which arc identical 
with regard to electrical equipment, feed the 
overhead trolley network. In each sub- 
station is a motor-generator consisting of a 
200 kw., 280 volt flat compound direct current 
generator direct connected to and on a com- 
mon bedplate with a iillll b.h.p., 6300 volt, 
form K three-phase motor, the set having 
three bearing-,. The switchboard consists of 
three panels of blue Vermont marble, and 
from left to right are as follows: 

Starting panel for motor with automatic 
oil switch. 

Direct current generator panel. 

Direct current feeder panel with voltmeter 
on swinging bracket. 

Transmission Line 

The three substations operate in parallel 
and arc supplied with three phase current at 
6600 volts, the transmission wires being No. 
hard drawn bare copper throughout and the 
total length of the transmission line six miles. 
A lightning arrester ground wire consisting of 
five Xo. 16 stranded galvanized wires is 
strung along the high tension line and stapled 
to the top of each pole. The distance be- 
tween poles averages 1.">II feet and tin- light- 
ning arrester wire is effectively grounded at 
approximately every fourth pole. 

There arc nine transpositions in the 
transmission line. 

Telephones 

Telephone lines connect the three ;ub 
stations, power hou e, offices, mine, etc., 
and arc run on the transmission line poles 
from the power lion,,- to the brakehead; 

thence following I he o\ erhead con itru 
to 1 he end of the tramway. Each loco 
i arries a portable ti le] '7. mi by meat 
which communication can be 

establi he. I with any of the points on the 
telephone ti( I work. 

Mine Working 

The nunc i . worked on I he bord and pillar 

. with ,i>. yard 
pillars. The coal is from 8 to 
thickness and lies in | varyiiu 

horizontal of i in s, the grades 



1.56 



GENERAL ELECTRIC REVIEW 



being all in favour of the haulage. The main 
drainage of the mine is also free, the haulage 
tunnel cutting the coal at its lowest point. 

The present output is 500 tons and upwards 
per day of eight hours, half of this quantity 
being mined by hand and half 
by machinery. The machine 
mining is proving the more 
LOmical, however, and ad- 
ditional machines will shorth 
be installed. The Company 
is at present working two 
"Sullivan" bord and pillar 
chain machines with six foot 
cutting bars, each machine 
being en by a 30 h.p. 

motor. These machines are 
the first of their class to be 
used in New Zealand and 
are giving excellent results. 

The machines arc cutting 
from three to four <> yard 
bords per shift, each bord 
producing on an average 
aln.ni 30 tons of coal. The 
undercut is made in the coal 
itself at the bottom "I" the 
seam. 



ings through 12 in. pipes which are run into 
the working places in place of brattice. 
These blowers are found very convenient 
and can easily be moved from place to 
place as required. 




Ventilation 



The mine is singularly free 
iY< mi explosive gases and the 
workings are so arranged that the ventila- 
tion] .i in q )lc proposition. The main work- 
ings arc at present in the "B" tunnel, 
which is ,' of a mile in length and runs out 
to daylight at each end. An electrically 
driven Waddel fan is situated at the top of 
a shaft in the center of the tunnel and 
draws air through the workings from both 
ends of the tunnel. At 290 r.p.m., the fan 
has a capacity of 80,000 cubic feet per minute 
at 1 1-2 in. waii and requires 30 b.h.p. 

to operate. It is belt driven from a 40 h.p., 
500 volt, three-phase motor, thi ingle- 

phase transformers for which are situated 
in No. 3 substation. The object in usii 
volt, three-pha irs for driving the fans 

in preference to operating them from the 250 
volt direct current trolley is that this service 
will he continuous irrespective of any possible 
interruptions to the trolley overhead net- 
work. In addition to this fan there are six 
"Sturtevant" blowers direct connected to 5 
h.p., 250 volt, direct current motors; these 
units being located at various points in the 
workings and used for ventilating the head- 



Tipple and Storage Bins, Showing Hydraulically Operated Doois 



Quality of Coal 

The coal is a good bituminous variety with 
a high calorific value and low pert i 
ash. swelling on heating and giving a fairly 
hard coke. On the opposite page an analysis 
of coal taken from "B," "C," and "D" tun- 
nels is given, which was made by the govern- 
ment analyst : 

From an inspection of these figures it will 
immediately be noted that the ash percentage 
is unusually low. It should, however, be 
taken into consideration that the coastal range 
from which this coal is obtained has other 
coals which arc also very low in ash, though 
test figures have hardly been comparable with 
the analysis given here. 

Tipple and Storage Bin 

The main bin into which the coal is de- 
1 at X.^akawau has a capacity of 5600 
tons and is divided into three compartments, 
two of 2( mi) tons each for the storage of 
unscreened coal and one of 1000 ton 
the storage of slack. The loaded tubs run 
into the bins by gravity and are thrown into 



THE WESTPORT-STOCKTON COAL COMPANY'S COLLIERY 



L57 



any one of the three tipples desired, whence 
their contents are discharged onto the dis- 
tributing jiggers or into bins as the case may- 
be. The slack from the screens is elevated 
and conveyed by a scraper conveyer to 
the slack bin. Through tap- 
pies are employed, the loaded 
tubs displacing the empties 
which automatically gravitate 
to the empty siding to be 
made up into a train for the 
trip back to the mine. The 
main bin is composed entirely 
of ironbark built on pile 
foundations and has five load- 
ing roads under it, from which 
the coal is loaded into the 
eight ton capacity govern- 
ment cars and conveyed to 
Westport. The loading doors 
work in a horizontal plane 
and are opened and closed 
by hydraulic rams which 
operate at a pressure of 120 
lbs. per square inch. Pressure 
is obtained from an accumu- 
lator operating from a 500 
foot head of water derived 
from a small stream near the 
top of the lower incline, the 
object of the accumulator 
being to maintain a constant 
pressure when the doors are operated. The 
scraper conveyer for elevating the slack from 
the screens, and the picking band for loading 
the screened coal, are both operated by one 
15 h.p. direct current motor. The two un- 
screened conveyer belts are each operated by 
a 10 h.p. motor and the distributing and screen- 
ing jiggers by 5 h.p. motors. The bins are 
lighted by two arc lamps and in addition by a 
number of incandescent lamps where required. 



Labour Conditions 

The supply of all classes of labour necessary 

for working the mine is fairly plentiful at the 
present time. Wages are regulated by the 
Arbitration Court, and New Zealand has 




Mark 



"B" 

per cent. 



Fixed carbon . 

Volatile hydrocarbons 

Writer 

Ash . 



' 


- 


per cent. 


per cent. 


61.85 


66.80 


36.45 


31.85 


0.95 


1.05 


0.75 


ii 30 



61.75 

36.80 

1 .25 

0.20 

100.00 100.00 100.00 



Coke (from closed re- 








tort) 


61.8 


i;i 90 


<;7.i(i 


Calories per gram . 


8182 


8183 


8139 


British thermal units 








per lb. 


117 is 


14698 


14650 


irative power per 








lb. ... 


15.24 




15.22 


Practical evaporative 








power per lb. (cal- 








culated on 60 per 








cent, efficiency) . 


9.19 


9.18 


9.13 



Distributing Belts 

practically been without a strike since the 
introduction of the "Arbitration ami Con 
ciliation Act," although recenlly there has 
been some signs of dissatisfaction on the 
part of the workers. 

Cost of Production 

A royalty of twelve cents per ton to be 
paid to the State, and the compulsory pay- 
incni to the "Government Compensatio 
Accident Fund" of one cent per ton, art- 
factors which must be considered in addition 
to the actual cost of production. 

Markets 

Up to the present there has been a full 
and evei increasing market within the 
Dominion for the West Coast coal, this section 
being the only part of the Dominion in which 
good bituminous coal has been found. I'm- the 
past ten years, the local tption has 

increased at the rate of 100,000 ton 
annum. Ten years ago the consumption 
was, roughly speaking, one million 
while at the present time it i illions, 

rather more than half of which is supplied 
from the We I ( oa rt coal fields. Thi 



158 



GENERAL ELECTRIC REVIEW 



with the exception of about 200,000 tons 

imported from New South Wales, is supplied 
from the Lignite & Brown coal seams which 
are found in various parts of the colony. 
Up in the present time, owing to the full 
home market, the foreign coal trade has not 




Entering the Tipple 

been exploited, but with the extension o 

mining on the Wesl Coast , ii may become 

:ary to look for an ov< i 
trade. The foreign markets com- 
manded through \V< t p ti arc: 

West Coast of South America. 
This, perhaps, is the most im- 
portant customer in the Pacific, 
and .1 i he chart shows 

that Westporl is 1 200 mile nearer 
than Australia. Australia exports 
alu'Ul 500,000 ton per annum 
to South Ac ;xl iii addi- 

tion, ■ hipments are fre q uently 
made from English ports and lat- 
terly from 1 )urban, 

Manila, Java, Sumatra, or in 
other words the Easl Indies, are 
perhaps the next in importance. 

There is a trong demand \ tt j I 

team and ga co I here. The 
Indian coal doe not by any mi 
satisfy the requirements and from 
three to four hundred : : 
tons are sent annually from Australia. 

Mexico,! 'ah lorni a and t In I l.iuaiian Islands 
are also, geographically peaking, close to 
New Zealand, and the West Coasl bituminous 
eoal must command an extensive market there. 



Harbour 

The Westport harbour is the most prosperous 
bar harbour in the Dominion, about half a 
million sterling having already been expended 
in improving the harbour and deepening the 
water on the bar. 

The port may lie safely 
worked by vessels drawing 
about IS feet of water. 

The expenditure of a new 
loan of £200,000 is expected 
to increase the depth of 
water on the bar and in the 
fairway to such an extent 
that ocean going tramp 
steamers of from 5 to (i thou- 
sand tons will be able to 
fully load. This will encour- 
age and render possible a 
much larger foreign trade 
than can be coped with at 
the present time. 



Electrical Equipment 

T!ie entire electrical equip- 
ment for this enterprise was 
furnished by the Australian 
General Electric. Company, 
and manufactured partly by the General 
Electric Company, Schenectady, U. S. A.. 



frill' 



* 




The Tipple 

and partly by the British Thomson Houston 
ty, Rugby, England. 
The writer is indebted to the Company's 
engineer for „•___„„ L securing th photo- 
graphs and assistance " e^ 
data tor this a"-: 1 'e- 



159 



COMMERCIAL ELECTRICAL TESTING 

Part VI 

By E. F. Collins 

Technical Superintendent, General Electric Company 



ROTARY CONVERTERS 
Preliminary Tests 

The cold resistance of the armature of a 
rotary converter is measured between the 
collector rings, as follows: 

For a three-phase machine, between rings 

^ 1-2,1-3, 2 -3 

For a two-phase machine, between rings 
1-3, 2 I 

For a six-phase machine, between rings 
1-4. 2-5, 3 6 

The resistance of the various phases should 
be the same and it is immaterial whether the 
rings are numbered from the inside or from 
the outside for this measurement. 

Running light on a rotary is taken with 
the machine running from the direct current 
end. With the brushes set on the neutral 
point, the direct current voltage is held 
constant and the shunt field varied until the 
rated speed of the machine is obtained. The 
input to both field and armature is then 
read. Since there is very little armature 
reaction in a rotary converter, the brushes are 
set on the neutral point before the machine 
is started. It often happens, however, that 
better commutation can be secured by shift- 
ing the brushes away from the neutral point 
very slightly. In case of unsatisfactory com- 
mutation, the brushes should be shifted in 

h direction, since some machines require a 
forward and some a backward shift from the 
hanical neutral. 

The determination of the ratio of the alter- 
nating current to the direct current volta 
is one of the important tests on a rotary, 
and care should be taken to secure accura i 

ilts. The converter may be driven from 
either the alternating or the direel currenl end 
and, in order to check the accuracy of the in- 
struments, t wo alternating currenl voll meters. 

potential transformers, and two dired 
rent voltmeters should always be used. 

During tlie te I 'lie direel currenl voltage is 
held constant and the alternating current 
■ een rings 1 and '.', on a tWO- 
1-ihase. and 1 and 1 on a six-ph; ie machine. 

1 hi rat to is taken al no load and at full load. 
and should bi as follows when the machine 
is running from the alternating current end: 



71..-) 


7:s 


71..". 


7:; 


7 1 7) 


62 5 

7:; 
36.5 


35.8 


til 


(', •_'..■> 



RATIO AC. TO DC. VOLTAGE 

X'. Load Pull Load 



Single-phase 

Two I'll. i ie i mea >ured on diam 
eter) 

Three-phase 

Six-pha e (measured en diam- 
eter) 

Six-phase (measured en adja- 
cent ring) 

Six-pha se I hum ured en alter- 
T 'ings) 



The amount of pole face arc will change 
the ratio. 

An easy and approximately correct method 
of telling whether a rotary is running with the 
proper shunt field excitation, is te note the 
ratio of the alternating currenl to the direct 
current, which should be as follows: 

Three-phase alternating current and direct 
current practically the same. 

Two-phase alternating current equal to 
three-quart crs of the direct currenl. 

Six-phase alternating current equal to one- 
half the direct current. 
Equalizer Taps 

As soon as a rotary is assembled and before 
any running tests have been started, the 
Spacing of the equalizer laps and the taps to 
the collector rings must be carefully checked. 
• teeasionally a wrong connection is made and, 
if it is not corrected before 'he running t< 
are started, one or more equalizer leads may 

become badly overheated or be burned off. 

Constant Ratio 

The standard shunt wound rotary converter 
has a very nearly constant itioo irnating 
to dired current voltage, o th fluctua- 

tion m the voltagi ot the alternating current 
supply will show direct h on the direct euro 
voltagi deln ered. Such machine i are un- 

i '< lien much variation in load 

urs. When the direct current volts have 
to be varied on a i trd machine, the im- 
pn i d alternat ing « me ust !»■ 

red. This is generally done bj u 
Iran o provided with dial switches.by 

mean ol which the | . o is 

ed. 



160 



GENERAL ELECTRIC REVIEW 



I f a scries field winding is added to the stand- 
ard machine, a practically constant voltage 
can be obtained with sudden changes in load 
by introducing reactance into the circuit, 
or in some cases by using the inductance and 

ance inherent in the feeder circuit. 
This is possible, for the reason that an alter- 
nating current passing over an inductive 
circuit will decrease in potential if lagging, 
and increase in potential if leading. 

A rotary converter running as a synchro- 
nous motor requires a certain definite field 

ation to effect t he minimum input current 
to the armature. Varying the excitation 
either way changes the input current, so that 
by using sufficient reactance in the alternat- 
ing current circuit from which the converter 
receives its power, the alternating current 
voltage at the converter terminals may be in- 
creased or decreased by increasing or de- 

ing the field current. By adjusting 
the shunt excitation of the compound wound 
machine to give a no load lagging current 
of about 2.~> per cent, full load current, and 
the series field to give a slightly leading 
curreni it full load, the impressed voltage 

■ load will be automatically lowered and 
full load increased. Hence a 
practical)}, col nit direct current voltage 
will be delivered at all loads. 

Variable Ratio Machines 

The split pole rotary differs from the 
ordinary rotary in that the poles consist of 
two separate and independent parts, each 
pro\idcd with its own field coil. The 
auxiliary pole may be placed on either the 
leading or the trailing side of the main field, 
i lit ions under which t he- 
machine is to operate. If it is to operate as a 
straight rotary, the auxiliary pole is to be 
placed on the trailing side; while if the ma- 
chine is to float on the line to take fluctuations 
of load through a storage battery, and hence 
run inverted part of the time, the auxiliary 
pule .should be on the leading side. The 
reason for this is as follows: The auxiliary 
ommutation when on the 
leading side, as well a ites 1 he 

current voltage, and will be of © larity 

for commutation if the machine inverts at a 
I current voltage corn-ponding to no 
excitation of the auxiliary poll 

In wiring a split pole rotary for test, the 
transformers used must be ex ictly alike. 
The best results are obtained by using trans- 
formers with two secondaries excited by one 
ary. Can- should be taken to see that 



the cables from the transformers to the rings 
do not differ in length or cross section, and 
that all switches in these circuits have their 
contact surfaces well cleaned with sandpaper. 
These precautions are necessary to prevent 
any unbalancing of the current in the alter- 
nating current circuits outside of the armature. 

The testing instructions should specify the 
manner in which the transformers are to 
be connected, both primary and secondary; 
the alternating current volts to be held across 
corresponding rings; and the range through 
which the direct current volts are to be varied 
by means of the auxiliary field. The follow- 
ing no load readings should be taken: 

Current per phase. (Must be balanced.) 

No load phase characteristic. 

Ratio of voltage. 

Volts between adjacent collector rings with 
main field only. 

A set of readings of alternating current 
amperes while varying the direct current 
volts by means of the auxiliary field through 
the total voltage range, the main field being 
he'd at minimum input value, the alternating 
current volts constant, and the brushes 
shifted to give the best commutation over the 
whole range. 

A s,t of readings while varying the direct 
current volts through the total range by means 
of the auxiliary field, the main field being 
adjusted to give minimum input for each 
change in direct current voltage. 

A full load ratio and the current per phase 
for minimum input, using main field only. 

Phase Characteristics 

Three full load phase characteristics should 
be taken as follows: 

1st. Holding the alternating current volts 
constant and using the main field only. 

2nd. At the lowest limit of the direct 
current volts: holding the alternating current 
and direct current volts constant and ad- 
justing the direct current line current to 
that value which gives the rated output for 
the mid voltage with zero auxiliary field. 

3rd. At the highest limit of the direct 
current volts: holding the alternating current 
and direct current volts constant and ad- 
justing tin- direct current line current to that 
value necessary to give the rated output lor 
the mid voltage with zero auxiliary field. 

Loss 

Three core loss tests are required to cover 
the various conditions of operation. These 
are made as follows: 



COMMERCIAL ELECTRICAL TESTING 



Mil 



1st. Core loss while varying the di 
.current volts by means of the main field only, 
with auxiliary field not excited. 

2nd. Core loss while holding the excitation 
of the main field constanl al thai \ alue which 
gives mid direct current voltage, and varying 
the auxiliary field to change the direct current 
voltage. 

3rd. Core loss while holding the alternating 
current volts constant and varying the main 
field each time the auxiliary field is changed 
'd change the direct current volts throughoul 
the range. This gives unity power factor. 

All other tests are made as on standard 
rotaries. 

Inverted Rotaries 

The speed of a rotary when running from 
the alternating current side is determined 
by the line frequency. The same machine 
running as an inverted rotary and delivering 
alternating current operates as a direct cur- 
rent motor. Its speed depends upon the 
field excitation and load, and it will deliver 
a variable frequency, particularly if com 
pound wound. When run inverted, a com- 
pound wound machine should have its si rii 
field almost, if not entirely, short circuited 
when part of its load is inductive, since a 
lagging current will weaken the field and in- 
crease the speed, sometimes causing a runa- 
way. For this reason care must always be 
taken when running a rotary inverted to ' 
that sufficient shunt field excitation has been 
obtained to prevent excessive speed, particu- 
larly when another machine is operating as a 
rotary from the inverted machine. 

Motor- Converter 

A motor-converter conGisl of a standard 
rotary converter and an induction motor. 
The induction motor lias a wound rotor with 
taps brought out to a set of common rings, 
which take the place of the collector ring 

both motor and ci >n\ erter. The volta 

the induction motor rotor is th 
current voltage oi the converter. The ad- 
vantage of the motor converter i I ha1 high 
tension currents (up to L3000 volts) ma 

applied to the induction motor, 

rotor delivering lov to the 

iter. Hence the intervening bank of 
ormers, alwaj s nece isary wit h a n 
required. No reduction od power 
is caused by the induction motor, ince unity 
power factor may be mai • il h th 

motor convi rter by the proper adjustment oi 
the field of the rotary. 



Starting Tests from the Alternating Current End 

The rotary should be wired to an alternal 
ing current generator of suffii ienl 

to Mart it without overloading. If trans- 
formers are needed ill order to gel I he © 

' i iltage, i he] should be placed between I he 
dynamometer board and the gi aerator 

A rotar; . "hen starting from the alternat- 
i I current end, is similar in action to a 
transformer. The armature correspond to 
the primary, and the field, which has a large 
number of terms, to tin- secondary. Hence 
the induced volts on the field may be ver\ 
high, often 3000 or mini volts. In all ca i 
therefore, the field connection must l>e broken 
in two or more places to keep this voltage 
within safe limits. A potential transformer 
and voltmeter should be connected across one 
or two spools in series for reading, the 
induced volts field, and a record made as to 
the number of poles included in the reading. 

Starting tests should be in. id. from several 
different positions of the armature with respect 
to the field. A scale, corresponding in Ieng h 
to the distance between collector ring taps, 
should l>e laid off on the armature and divided 
into five equal parts. A point of reference 
is then marked on the field, opposite to which 
the marked positions of the armature are 
placed for the successive starts. 

Having broughl poinl No. 1 opposite. the n 
erence point tin- alternating current switche 

hould fe closed and the field on the alter- 
nator increased until about one-half normal 
full load current is sent through the rotary, 
reading volts and amperes in the various 
phases. As it is impracticable to read all 
phases al once during the start, the amn 
should be cu1 into that phase which shows 
the highe t current and the voltmeter acros 
the phase which indicates the highest vol- 
in order to gel the maximum readings at 
the instanl of starting. The field of the gen- 
ii should be increased until the armature 
to revolve, when volts and am 
input and induced volts on the field should !"■ 
n ad. The voltage acri i is t he colli ■ 

l Id I hen be held com i ant until the n 

reache ynchronism, the time requii i 
reach 'In point iron, the itart In inc. noted. 

Then an everal methods of determining 
whether the rotary is in synchronism; one. 
by the fact thai the induced volts field will 

fall to zero; another, tl 

icro the armal ure will read a definite vol- 

which will vary from a negative to a 

positive reading if the rotar) is below syn- 



L62 



GENERAL ELECTRIC REVIEW 



chronism. Readings of volts and amperes 
should be taken on all phases after the rotary 
has reached synchronism. The machine 
should then be shut down, the armature 
brought to position No. 2, and the test 
repeated. In this manner all five points 
should be tested. After these tests have 
been mad.', the- time required to bring the 
rotarv to synchronism should be taken by 
throwing one-half voltage across the collector 

Starting Tests from Direct Current End 

When starting from the direct current end, 
the rotary must be wired to a direct current 
generator of am] icity. The rotary 

should be separately excited with a field cur- 
rent corresponding in value to that for no 
load at minimum input I unless full field is 
ilicdi.and the voltage across the armature 
brought up gradually by increasing the field 
on the driving generator, until the armature 

I to revolve. The voltage should then 

dily increased at thai rate which will 
bring the rotary to normal speed in approxi- 
mately one minute. This rate can be found 
!r trial, and when once found, the test should 
be repeated once or twice to make certain 
that the results are correct. 

Phase Characteristics 

No Load. If the phase characteristic tests 

follow a heat run in which an IRT regulator 
has been used, it must be disconnected. The 
most satisfai tnbination is to run two 

converters for this test, the one under b 
running as a rotary and driven by th 
running inverted with a direct current loss 
supply. T 1 and the direct current 

voltage are held constant by varying, respi 
tively, the field i verted machine and 

the voltage of the loss supply. It musl 
remembered thai a lagging current will 
increase the speed of the inverted rotary, and 
therefore the inverted machine should be 
watched constantly so long as the current la :4s. 

With the held excitation of tl 
reduced to the lowe permitted by the 

inverted machine, the alternating cun 
aim d VOltS line and the direct cm-rent 

and volts Held should be read. As 
stated above, the speed and the direct current 
volts arc held constant throughout the ' 
The field cuirenl of the rotary is increased by 
small increments and readinj sabove. 

The alternating current amperes input will de- 
crease rapidly until the minimum input point 
is reached, when they will incn gain. 



The field excitation should then be increased 
until the input current has a value of at least 
half the full load current of the machine. 

Full Load. The full load characteristic is 
taken in exactly the same way as for no load. 
The direct current volts are held constant at 
normal rating and the amperes output con- 
stant at full load value. The field excitation 
is varied through nearly as possible the same 
range as for no load characteristic. The 
readings taken are, for the alternating current 
side, volts and amperes; and for the direct 
current side, volts armature (held constant), 
amperes output (held constant), volts field, 
and amperes field. The speed is held con- 
stant. 

Compounding Test with Reactance 

When a rotary is required to automatically 
deliver a constant direct current voltage under 
a load subject to sudden changes, a compound 
wound machine is used with a definite react- 
ance inserted between the rotary and the 
line. Such reactances must be tested with 
the machines for which they are designed. A 
constant voltage is possible, since an alter- 
nating current passing through a reactance 
will increase the potential if leading, and de- 
crease it if lagging. By adjusting the shunt 
field so that about 20 per cent, lagging current 
flows at no load, the strength of the series 
field can be adjusted to give a slightly leading 
current at full load and thus maintain a con 
stant direct current voltage. A compound 
converter operating with reactance in circuit 
must be compounded like a direct current 

aerator. Unless otherwise specified, the 
voltage of thi' alternator driving the rotary 
should be held constant and the shunt field 
adjusted to give the correct no load 
voltage; when, without touching the field 
rheostats, full load should be applied and tin- 
direct current volts read. If the machine 
over-compounds, hi ■ ries field is too strong 
and gives too large a leading current, in which 
a shunt must be adjusted across the 
terminals of the series winding to shunt a 
portion of the current. In this compound 
test all readings are taken and all adjust- 
ments made without touching the field rheo- 

ll after the no load adjustment is 1 ffected, 
■ asc of a direct current generator. 

Pulsation Bridges 

Since the torque of a rotary only needs to 
be great enough to overcome the mechani 
3es,the machine is very sensitive to chan 
in line conditions; i.e., excessive line drop or 



COMMERCIAL ELECTRICAL TESTIXC 



163 



speed changes of the driving unit. In many 
cases the line drop alone will start a rotary 
pulsating, and once started the pulsating 
generally increases rapidly until the rotary 
falls out of step or flashes over. To prevent 
pulsation, copper or brass bridges, which act 
as short circuited secondaries and prevent 
sudden changes of the input armature current, 
arc placed between the poles. Rotaries of 
new design are tested for pulsation by insert- 
ing a definite resistance in each phase between 
the machine itself and the driving alternator. 
The drop through this resistance corresponds 
to the line drop which will probably occur 
in practice. Usually 15 per cent, drop is 
assumed and the resistance per phase neces- 
sary to produce this is determined from the 

, . (A.C. voltage)- 

formula ,, ir .„- Xper cent, drop = rc- 
Kw. xlOOO 

I ance. If two rotaries are tested together 

each machine should have 15 per cent, drop 

ween it and the driving alternator, or 

30 per cent, between the two rotaries, as 

shown in Fig. 29. 

With the two machines running in syn- 
chronism, self-excited, and with the fields 
adjusted to give minimum input, observe 
the direct current voltmeters on the two ma- 
chines. Any slight pulsation will be shown 
by these instruments at once. The direct 
current volts should be held constant on one 
machine throughout the test. Now, with the 
field current on one machine held at minimum 
input value, the field current on the other 




Dynamometer 
Board 

Alternator 
4 4 4 



Resistance 




Resistance 



Connections for Pulsation Test on Rotary Converter 



machine should be reduced to aboul om 
minimum input value. If no | lsation is 
noted, a full set of readings should be taken 

on both machines, reducing the field cum 



the other machine to one-half minimum input 
value and watching for pulsation on both 
machines, which now take a heavy lagging cur- 
rent. A full se1 of readings under these condi- 
tions should be taken. The field of the first 
machine is again adjusted to the minimum 
input value, readings are taken, and pulsations 
watched for. With this field held at minimum 
input, the field of the other machine should 
be changed from its value of one-half mini- 
mum input to twice the minimum input value, 
readings and observations being made as be- 
fore. The other field should then be brought 
up to twice normal value, readings taken, and 
the effect of the heavy leading current in each 
machine noted. Leaving one field over-ex- 
cited, the other field should be weakened to 
give minimum input, and a full set of read- 
ings taken. If no pulsation develops with 
the high line drop under these extreme 
conditions, the machines arc satisfactory. 

Input-Output Efficiency Test 

Input -output tests on small machines 
(300 kw. or less) arc made with the machine 
running as a rotary, dead loaded on a water- 
rheostat. Larger machines are tested in 
pairs, one machine pumping back on the 
other with an electrical loss supply. The 
machines are wired in a manner exactly 
similar to that used in a pump back heat run 
(circulating power heat test), special atten- 
tion being given to the wiring to see that no 
unbalancing occurs on cither the alternating 
current or the direct current circuits. With 
the machine running as a rotary, wattmeters 
are connected in the alternating current end. 
between the rotary and the transformers, and 
preparatoins made for reading direct cur: 
armature and field amperes and volts. If 
current transformer are used with the watt- 
duplicate Iran former must be used 
in the other phases of the machine to pre. 
unbalancing caused by the resistance and 
inductance of the transformers. With the 

ichine running in synchronism at rated 
nd zero load, and all mi 
the alternating current vol I on 

hould be held coi < are- 

f u l en .,1 all mini: The 

in each phase should 
read as a check on the wiring and balancing 
All instruments should also be 
carefully checked for itraj fields and any 

ie must be pro- 
ted by iron shields, or their location chai 
ed. With full load, the iy field 

mid be repeated, tince any instrument 



164 



GENERAL ELECTRIC REVIKW 



affected will give misleading and erroneous 
results. With the no load minimum input 
field current held constant, the alternating 
current input, as shown by the wattn. 
should be carefully read as a check on the 
no I lad losses. 



!■* 



t 



1 






























-_L 




























\ 






























SI 






























k 




























\ 




























-« 






















































































= - 










I 












1 



2000 3000 

Feet per Af/r?t/te 



Fig. 30. Coefficient of Friction of AC. Brushes 

A: efficiency is usually guaranteed at I. 
5, 4, 1 and 1} full load, careful readings must m> 
ik'en at these loads. Each time the load 90 
is changed, the rotary field excitation must 
be changed to the minimum input value for 
that load, which is shown when the sum oi-J° 
the wattmeter readings is exactly equal to the \eo 
lev a. input. To obtain this condition for$ 
each load, several trials and considerable timejv:'* 7 
is usually required, so that an efficiency tcstV" 7 
made in this way is more expensive than one*^ 
made by the separate loss method. The 
likelihood of error is also greater. This ^ 
method, therefore, is not satisfactory for 'o 
rotary efficiencies at other than full load. 

The method employed to calculate the ' 
efficiency of a standard rotary converter is 
similar to that used for direct current gener- 
ators, except for the additional ("R and 
friction losses of the alternating current « 
brushes. Because of the neutralizing action 
of the motor and generator currents it should 
lie noted that Only a certain percentage of 
the current as given by the instruments must 
be used for calculating the ("R loss in the 
armature. This percentage varies for dif- 
ferent machines as follows: 



For Single-phase . . . .1.00 
Two-phase . . .72 
Three-phase. . .!>4.'-i 
Six-phase 472 

As with the direct current brush resistance 
a curve of the alternating current contact 
resistance must be referred to and no direct 
measurement of resistance attempted. In 
every case the contact resistance per ring 
should be calculated, the total loss being 
obtained by multiplying by the number of 
rings. 

Brush contact area per ring = width of 
brush in inches x arc of contact in inches ■ 
the number of brushes. 

The brush density per ring = 
Alternating current 
Brush contact area per ring 

The resistance obtained from the curve 
corresponding to this value, divided by the 























4- 




— r- 






4-j 


-!— 










IF 


■• 




ft 




r 


— 


r 






— 


-if- 






-jg 






/ 


j> 






S 




<S 




i 








N 
S 


i 






si 


. «_ 


t- 




N 


\ 




!w_[ 






■ Y -;> 




^ 








> 






s: 


* 










■■- 












i? 


















/ 






;» 














































/ 






















































/ 
























































_J 












































































































/ 





















































































































































































































































































































































































































































































































.V 



I, 



Six-phase 






20 



60 SO 

Fig 31 a 



/20 



The calculation of the alternating, current 
brush contact resistance requires a measure- 
ment of the alternatinj Bowing in the 
armature, which varies in differ Ql typ 
machines. The following arc the coi 
which the direct current should he multiplied 
to obtain the alternating current. 























' — 




— 






















' 




































































































A 
















































^ 
















































¥ 


I 
















































IS 


















































^ 






















' 








F \° 


is 




? 






£ 




























g4 








<1 


























.._ 




\ 






% 
























*~~~~~ 


—*H 






\ 








«' 


















— <— 






3 




^ 




































\ 










*i\ 


























,, 




s 




























$ 


y 










3i 




1 


























uH 










i_ 
























£L 


g 


&f 














Briisn Friction £IC. 


Core 


loss . _, 


















\ i T r 


e Friction - 1 ^ 














B 


xaA 


T ~ktian/1.C 


%t 


■ - 




tfi 


'/PSrcxsnesAC 




,C.F.Fie/J — 
■ , 1 




\Vf 




:r-ss 




_L 






_ 


— 


- 






































4 


— 




- 


— 



20 -to eo so /oo /to /4a 

Fig 31. Efficiency and Losses on a 750 Kw . 600 Volt. 
750 R.P.M . 25 Cycle. 3-Phasc Rotary Converter 



COMMERCIAL ELECTRICAL TESTING 



165 



TABLE XII 
EFF. AND LOSSESIOF A 300 KW.,600 V., 4-POLE, 25 CYCLE 3-PHASE ROTARY CONVERTER 



', Load . 


1) 


2.. 


.".ii 


i ■> 


100 


1 25 


150 


Volts Line 


600 


Til III 


600 


600 


nun 


600 


600 


Amps. Line 


n 


1 25 


251 1 


. 


500 


ii.'.". 


77.(1 


Amp-.. Shunt Field 


2.65 


2.65 


2.65 


2.65 


2.65 


2.65 


2.65 


Amps. Arm. D.C. 


2.65 


127.6 


252.6 


377.6 


502.6 


627.6 


752.6 


Amps. Arm. A.C. 


— 


122.5 


2 1 2 5 


362 


182 


602 


722 


( " iri Loss 


4760 


1760 


I7r.ii 


1760 


4760 


4760 


1760 


Brush Friction D.C. 


1134 


1134 


1 134 


1 134 


1 134 


1 134 


1134 


Bearing Fricti. in 


I'll .".4 


2654 


2564 


2654 


2654 


2654 


2654 


( "-R Armature 
















.585 <D.C. C-R. 


II 


207 


1046 


2340 


U in 


6450 


91 


<"K Brushes D.C. 


(1 


1 1 ).", 


:; in 


641 


960 


1280 


1720 


CR Shunl Field 


til in 


900 


! 


900 


900 


900 


900 


t"-'R Rheostat 


690 


690 


690 


690 


690 


690 


r.t hi 


CR A.C Brushes 


— 


17 


7:; 


161 


286 


l 16 


7)77. 


C'R A.C. Brush Fric. 


I'll 


I'll 


211 


21 1 


211 


211 


21 1 


Total Losses 


10349 


10738 


1 1 SI IS 


13491 


15735 


! 8525 


21944 


Ew. < )utput 


— 


, ."i 


150 


225 


300 


375 


l.-.ii 


K\v. Input 


10.3 


85 . 7 


161.8 


238.5 


315.7 


393.5 


471.9 


' ,' Efficiency 





S7.1 


92.7 


94.3 


95.0 


95.3 


95.4 


Brush Den-' A.C. 


— 


10.45 


19.9 


29.8 


39.6 


19 5 


59.3 


site D.C 


— 


8.5 


6 


25.2 


13 6 


11.9 


18.2 


Brush Contact / A.C 


— 


.00123 


00123 


.00123 


.00123 


.00123 


.mil in 


Res,- ( D.C 




.0062 


00534 


00451 


0038 


00326 


.00304 



Resistance of Armature D.C. End 25° C. .0243 Ohms, Warm .0280 ohms at 65° C. 

Resistance of Shunt Field 25° C. 111.3 Ohms. Warm 128. Ohms at (15° C. 

Dimensions of Brushes/ X |><1| arc (AC.) X., of Studs 4 D.C. 12 A.C. X,, per Stud 8 D.C. 1 A.C. 

I ; a 1 i ( 1J.C . ) 

r 1 5 \ " 1 1 1 

Brush Contact Area. One Side ' ;, . ,. ... did .. i i i, . 

12.2 (A.( .) Sq. In. Brush Pressun 2 Lbs per Brush. 

Coeff. of Friction =.2 D.C. Coeff. of Friction =.12 A.C. 



Iirush area per ring, is the contact resistance 
per ring. 

The alternating current brush friction 
should be calculated in the same manner 
as that for direct current measurements, the 
coefficient of friction being taken from a 
curve. (See Fig. 30. 

Table XII and Fig. 31 show the form used 
in calculating and plotting rotary converter 
iencies. 

Normal Load Heat Runs 

When loading a rotar) converter on a v 

l hat all cables from the trans- 
ers ti> dynamometi r boards and to the 
alternating current rings o machine 

are Hi' the same length and capacity, and 
all contacts arc cleaned and bright 

Equal re i tance pet- 
will thus be obtained and unbalancing 
in the alternating current circuits exti 
to the armature prevented. In wiring the 
direct current circuit . field and its 

are disconnei 
When wiring rotarie . a in the case oJ all 
other high current direct current 
both idi ' he circuit should be laid 

together. No iron, such a 



tal or a section of the frame, must lie within 
the loop of the circuit, since it will become 
magnetized and materially affect the opera 
lion of the machine and instruments. I )i 
vide the shunt field into at least four sa 
by a "break up switch," which must always 
be open while starting from the alternating 
current end; since, due to transformer action 
and the relative number of turns of the field 
and armature, a high voltage is induced in 
the field at startin 

Always wire the positive ring of the rotary 

through a breaker to the blade of the water 

box. and thi negati - mic to the b< ix itself. 

Connect enough boxes in multiple to limit 

CUrrenl per box to about HID amperes 

maximum. Make provision for reading al- 
ternating current at ndvoll armature, 

direct current ampere, and volt . arm. 
amperes and volts field, and th peed ol 
alternator. 
To tart the machine, close the alternating 
current line switche! and the field switch ol 
ernator, incn lie excita 

tion of the alternator and keepit atch 

on tb ut in l In- alien irrellt 

If this 150 pel- 



166 



GENERAL ELECTRIC REVIEW 



normal before the rotary starts, cheek over 
the wiring. If the machine starts rotating 
in the wrong direction, reverse two of the 
leads on the primary side of the transformers. 
After starting, as soon as the alternating cur- 
rent drops to the minimum value I showing that 
the machine is in synchronism^, and the alter- 
nating current volts become normal, close 
the field "break up switch." If, after closing 
the shunt field switch, the brushes begin to 
spark, the residual magnetism left in the 
poles by the induced voltage at starting is of 
the wrong polarity. 

Two methods can be used to correct this; 
First, reverse the field with respect to the 
armature; or second, reverse the residual 
polarity by opening the alternator held circuit, 
and then closing this circuit and bringing the 
rotary back to synchronism, repeating the 
lion if necessary until the field builds 
up in theright direction. This second method 
is the more satisfactory since no change of 
wiring is required. 

Before proceeding further, read the cur- 
rent in each phase to make sure that there 
is no unbalancing. These currents should 
not vary over 1 per cent, from the average; 
any greater variation due to wiring must be 
remedied at once. After balance is i 
fished, the no load and full load phase 
character! tics are taken. 

These operations complete the preliminary 
tests and the full load heat run may now be 
made, care being taken to set the brushes for 
the best commutation. For the load run, 
hold full load direct current amperes and volts 
constant with minimum input field cur- 
rent. The load should be kept on at least 
one hour after all temperatures are constant. 
At the end of the run, temperatures must be 
taken on all parts of the machine and the 
resistance measured on the armature (alter- 
nating current end) and field, [f the rotar} 
machine, the armature resist- 
ance is measured between rings 1 1, '2 5, 
3-G, counting outwards from the armature. 

If an overload run is required, take a few 
points on the overload phase characteristic 
bo determine the field current required for 
minimum input; then hold this current and 
the direct current volts and ampi tant, 

as on the m irmal load run. 

After the heal runs, the tests should be 

finished by taking a phase rotation, hot drop 

on spools, direct currenl run 'it at 

ind direct current starting 

tests. 



ELECTRICITY ON THE FARM 

By John Listox] 

For the economical application of power 
to the various farm operations that are now 
to a very large extent carried on by mech- 
anical means, electricity offers so man} 
advantages for this particular service as 
compared with other sources of power that 
it stands pre-eminent. Its unqualified 
success on those farms where it has been 
adopted indicates that it has become a factor 
of such importance that it must now be 
seriously considered as affecting both the 
cost and quality of the products of the 
modern farm. If we compare electricity with 
other forms of applied power we find that 
its chief advantages are reliability, safety, 
cleanliness and flexibility in application. 

Owing to the necessarily scattered location 
of the buildings on the average farm, the cost 
of power when applied by means of separate 
engines (except in isolated cases which can 
properly be considered as special) is practi- 
cally prohibitive. At the same time, the use 
of such engines would add appreciably to the 
fire risk, which is a consideration of more 
vital importance in farming than in any 
other industry owing to the absolute depend- 
ence, as a rule, upon relatively limited local 
fire fighting facilities. When electricity is 
used for power and lighting the fire risk is 
reduced to a minimum. 

In the application of electric power the 
relative location of the buildings is im- 
material, as motors can be installed in each 
building or group of buildings and the current 
transmitted 1>\ means of wires from a central 
generating plant, which may be erected 
either on the farm or at a distance from it. 

When planning the electrification of a farm, 
it should be remembered that as the service 
required of motors for farm work is in nearly 
every ease intermittent, the periods for 
operating the various units can be so arranged 
that at no time will all of the motors or even 
a large proportion of them be in operati 
simultaneously. 

This condition will in most cases allow the 
installation to be so designed that a small 
generator can supply ample current fo" a 
relatively large number of motors, ha\ i 
an aggregate capacity greatly in excess of 

that of the generating plant. As a 

quence the cost of generating current for a 
given capacity in motors for farm work is 



ELECTRICITY ON THE FARM 



L67 



usually much lower than 
that involved in other in- 
dustries. 

The use of electric motors 
does not involve the neces- 
sity of employing skilled 
men to operate them, for, 
i >wing to the simplicity of 
the controlling devices, the 
average farm hand can 
start and stop them and 
control their speed without 
danger of injury to himself 
or the apparatus. 

Local conditions must 
always affect the selection 
of a prime mover for the 
electric generators, and 
ci impact generating sets for 
utilizing steam, gas, gaso- 
line or water power can 
now be readily procured. 
Where streams of sufficient 
head and volume exist in 
the vicinity of the farm, 
they may easily be con- 
verted into economical pro- 
i hirers of electrical energy 
by the construction of 
dams and the installation 
of automatically governed 
wa ter turbines. Many 
streams have in recent 
years been utilized in this 
way with entire success, 
both as to cost and ser- 
vice rendered, even on 
comparatively small farms. 

As an interesting demon- 
stration of the value of 
electricity on the farm, the following descrip- 
tion will appeal to every practical farm 
manager. 

A.1 Chazy, X. V., near the western shore of 
Lake Champlain and at about 15 

miles north of the city of Plattsburg, there 
is located a modem stock and dair farm 
which, in its operation, exemplifies the mani- 
fold advantages to be derived from the use of 
ricity for lighting and fur the various 
power requirements <>( the farm. 

This farm, which is owned by Mr. W. H. 
Miner and is called "Heart's Delight", i 
centrally Located across the bordei line of 
iplain and Chazy townships in Clinton 
County, as shown in Pig. I, and covet an 
area of 5160 acres. The nucleus of the 







Map Showing Location of Heart's Delight Farm and Streams from which it 
Derives its Hydraulic Power 



nt farm consisted of the old Miner 
homestead of L50 acres, which is now entirely 
unrounded by the land subsequently 
quired. 

Of the total farm area, aboul 1200 acres 
are under cultivation, another L200 
used for pasturage, and i he remainder i 
woodland. The outpul consists of live 

and dairj pn idud :; all cri >p i gri ra i 

farm being fed to the st< »1. and onl j fin 
producl hipped out. 

Th : o 1: include teron 

and Belgian hor ;es and pure bred horl 

Durham and Guernsi ■ lal atten- 

; given to 1 he raising of "Di ■ 

for breeder i and hi i1 house lamb ;, 

and hogs for ind the p m of 



168 



GENERAL ELECTRIC REVIEW 



sausage, hams and bacon. There is a con- 
siderable number of poultry and squabs, 
and a well equipped fish hatchery is de- 
voted to the propagation of trout. The 




View of Tracy Brook Power House and Beginning of Direct Current 
Transmission Line 



quality of the materials shipped is indicated 
by the fact thai practically the entire output 
.,f the farm goes directly to the Waldorf- 
Astoria and to other high-grade hotels and 
clubs in New York, Washington and Chicago. 

About three years ago il 
was decided to provide the ^^ 
farm with electricity for light 
and power, and the results 
have been so uniformly satis- 
factory that the equipment 
has been increased from time 
to time, some novel applica- 
tions having resulted owing 
to the energy and initiative 
of those charged with the 
management of the farm. 

Sufficient water pi iwer was 
found On thi farm itself to 
provide a cheap and reliable 
source of electric energy. 
Two streams pass tie 
the southern portion of the 
farm, as shown in Fig. 1; the 
smaller one being known as 
Tracy Brook and the I 

the Chazy river. 
It was found that thi 
streams were both fed by numerous active 
springs which, together with the drainage 
area afforded by the Adirondack foot hills. 
insured a dependable flow of water that 



could readily be conserved by the con- 
struction of dams. 

Across Tracy Brook three small concrete 
dams were built, thereby forming three ponds 
and giving a total reservoir area of 
about 170 acres. A concrete penstock 
44 in. inside diameter and 670 feel 
long carries the water from the reser- 
voir to a power house compactly con- 
structed of concrete, and so located 
as t<> obtain an effective head of Id feet. 

The power house equipment consists 
of two reaction water turbines, auto- 
matically governed and direct con- 
nected respectively to one 30 kw. and 
one \2h kw., 220 volt direct current 
generator. The current is transmitted 
over a pole line lj miles long to a 
central station located in the main 
group of farm buildings. 

About a mile below the power 
house Tracy Brook joins the Chazy 
river, and the tail race water from the 
Tracy brook station adds to the volume 
of water in the Chazy river reservoir, 

which is formed by a dam across the river a 

short distance below the point of confluence 

of the two streams. 

The Chazy river is about .'in miles 

long and empties into Lake Champlain; 




Interior View of Chazy River Power Station. Showing General Electric Alternating 
Current Generator Belts Connected to Water Turbines 



it has a considerably greater volume than 
Tracy Brook, and it was found that by 
building dams ample storage water and an 
effective head of 30 ft. could be obtained. 



ELECTRICITY <)X THE FARM 



169 



It was therefore decided to construct two 
concrete dams and a second and larger power 
house to supplement the Tracy Brook station, 
to provide current for the rapidly extending 
electric power applications at the farm. 

After passing through screens a1 the 
intake gate-house (which forms part 
of the lower darn), the water is carried 
to the Little Chazy power house 
through a concrete penstock 48 b) 60 
inches inside diameter and 630 ft. 
length. Attliepowerliousc.it enters a 
concrete flume provided with control- 
ling gates and is led directly to the 
water turbine wheels by short steel 
pipes. 

There are two turbine belts con- 
nected respectively to one 50 kw. and 
one 1(1(1 kw., 2300 volt, (in cycle, three- 
phase General Electric alternating 
current generators. The current is 
transmitted at the generator voltage 
over a single circuit pole line 2| miles 
long, to the power station at the farm. 

In the hydro-electric development 
the work has been carefully and thor- 
oughly done, so that the danger of 
interrupted service has been reduced to 
a minimum. The concrete penstocks 
are reinforced with steel bars, both hori- 
zontally and vertically, and are covered 
with earth embankments. The tail water 
from the Chazy river power house is carried 
by a canal to some distance below the station 
before being returned to the river, in order 
to secure the full benefit of the available head. 
The turbine governors are arranged for both 
hand and automatic control, and in addition. 
the governors at this station are also 
provided with emergency motor-operated 
mechanisms, controlled from the switchb 
Telephone wire, arc carried on the trans- 
mission pole lini . establishing communi- 
cation between the power hou le and the 
ral station on the farm. 

The Iran mis lion line polos arc of i 
with fir cross-arms, and are lined with pin 
insulators; they are from 35 to 10 feel high 
and are spaced at an avei aboul 120 

Thi i i inductor are I iare i opper wire, 
00 HAS. ' cd for the Tracy Brool 

line and No. 2 R.&S. for the ('hazy river 

An auxiliary of the hydraulic equipment 
of two hydraulic ra 
from the Tracy Brool i and pumping 

r to a 60,000 gallon I i i ed Km ft. 



above the ground on a steel tower erected al 
i he farm f< >t fire protection. 

As staled above, both the direct Current 
Tracy Brook power house and thi all ' 
nating current Chazy river power house 




View of the Alternating Current Transmission Pole Line 

iced into a power station at the farm, where 
the equipment includes a six-panel switch 
board and two motor-generator sets of 
General Electric manufacture, and a storage 
battery. 

Nearly all the motors used on the farm at 
present arc direct current machine . operating 

on I 1(1 and L'L'O volt circuits, and in order to 
supply the IK) volt motors and the lighting 
circuits, and to charge the Storage battery, 
the current which is received from the 
Tracy Brook power house al 220 volts 
direct current is stepped down by mea 

three-unit, I inn r.p.m., direct currenl n 

ni rator ;e1 , con :i iting of: 



220 volt 

wound 



direct current motor, 



i Ine 25 kw. 

conn ii mnd 

One '-'"i kw., I lo volt, direel currenl gener- 
ator, compound wound 

i Ine 12 kw.. 1 Id 150 volt, direct currenl 
in wound 

The alternating current from the Chazy 

ed at 2300 volts, 

I ili.i .i , HP ; iped do' 

! 10 olt through hree 10 kw. tyj 

i ran formers. ] ' lirect 



17H 



GENERAL ELECTRIC REVIEW 



current by means of a four-unit, 900 r.p.m., 
motor generator set, consisting of: 
One 100 h.p. synchronous motor 
One 7"> k\v.. 220 volt direct current gener- 
ator, compound wound 




Interior of Power Station at the Farm, Showing Switchboard pnd Motor Generator Sets 

One 75 kw., llo volt direct current gener- 
ator, compound wound 

One 11' kw.. Ill) L50 volt generator, shunt 
wound 

These two sets are interconnected by means 
of switches in order to insure continuity of 



service in the event of a shut down of either 
i if i he hydro-electric stations. If the incoming 
direct current supply is interrupted, the 
alternating current — direct current motor 
generator set can replace it. Vice vers 

the incoming alternating cur- 
rent supply fails, the 220 volt 
direct current unit of the 
alternating current — direct 
current set is operated as a 
motor, and the synchronous 
motor is then utilized as an 
alternating current gener- 
ator. 

On both of the motor gen- 
r sets the 12 kw. units 
are used for charging the 
storage battery, which 
sists of 52 main and 13 end 
cells, and has a capacil 
600 ampere hour-. The bat - 
tery is used as a balancer, 
and for lighting and power 
after 9:30 p.m., at which 
time the hydro-electric 
plants arc shut down. 

An interesting featui 
the farm power station is an 
electrically operated instrument which iscon- 
d with a weather station located on one of 
the fire tank towers and automatically records 
on a cylindrical chart a continuous record of the 
siieed and direction of the wind, the amount [of 
moisture in the air. and the precipitation. 



MOTOR DISTRIBUTION 



to. 


H P. 


R P M 


Department 




1(1 




1 ).iiry Barn 




•> 


1100 


I i.nry Barn 




u 


1350 


1 lairy Barn 




i;. 


2000 


ry Barn 




3 


1440 


Butter Making 


■J 


20 


650 


Refrigerating 


2 







rigerating 




71 


1500 


Refrigerating 




25 


e 


Grist Mill 




4 




Sau 




■• 


1100 


Barn 




lj 




Sheep Barn 




'> 


750 


Hatchery 




n 




\Y< lodworking 




n 




Woi idworking 




5 


1650 


Woodworking 




5 


1650 


W !w i .rkinK 




3 


." L500 


Machine Shop 




■ > 


1 LOO 


hine Shop 




."> 




Water Supply 




:; 


685 


Laundry 




•1 


1 Kid 


Laundry 




1 

-■ 


.-,:;.", 


Laundry 



Service 



II . Hoist 
Root Cutter 

una Pump 

•n Separator 
Butter Churn 
Ammonia Pumps 
Brine Circulating Pumps 
Centrifugal Water Pump 
Milling Machinery 
Meat I : 

Root Cutter 
Rout Cutter 
Fish Food Grimier 
30 in. Band Saw 

W 1 Surfacer 

Circular Saw ami Boring Machine 

W 1 Planer 

Engine Lathe 
30 in. Drill 
Triplex Water Pump 
line 
■ vcr 
Mangle 



ELECTRICITY ON THE FARM 



171 



The steam boiler capacity 
at the farm station is 120 
h.p. Steam is used in the 
various farm buildings for 
heating, for cooking food for 
the animals, and for the 
operation of air and circula- 
tion pumps. There is also a 
vertical engine direct con- 
nected to a 22§ k\v., 11(1 150 
volt direct current generator, 
this set being ordinarily held 
as a reserve. 

It will be seen from the 
foregoing that, in planning 
the farm equipment, every 
effort has been made to in- 
sure the continued mainten- 
ance of the electric service. 
That the precautions are 
fully justified by the benefits 
derived from the electric ser 
vice in the saving of time 
and labor, and the possibility 
of carrying on all indoor 
work under safe, well lighted 
and sanitary conditions, will 
be fully appreciated from the 
following description of the 
varied motor applications. 

The motors are distri- 
buted among the different 
buildings as shown in Fig. 2, 
and in most cases no special 
foundations have been re- 
quired, since one of the 
advantages of motor drive 
for farm machinery is the 
fact that the motors usu- 
ally required for this ser- 
vice are relatively light in weight and may 
be mounted either mi tin- machine 11 < H or on 
iloor, wall or ceiling. 

In the main dairy barn a motor driven 
hay hoist is installed, to which is . 
direct a Hi h.p. mot or, a simple drum control- 
ler being used to regulate the hoisting 
The load of hay is driven in onto the main 
Boor of the barn and stopped under an 
opening to the loft, located in the center of 
the building Two U-shaped forks are 
ed in the hay by the driver and the 
is started l>\ a man in I he lofl and the 
entire load elevated therel >, > ; 
"Her being so placed a 

I he operator an unin 
view. The hoist pulley is I ically 




Plan of the Main Group of Farm Buildings. Black Dots Indicate Location of Motors 



tripped, and the load of hay thereby trans- 
ferred to an overhead rail, along which it is 
pulled by the hoisi t • . the position ., \ 
for it in the loft. The forks are next rel( 
by pulling two light tripping ropes and the 
hay is deposited on the loft floor, the hoi I 
tackle returning for the next load. The 
entire operation is carried on by two men 

and .i ton of hay can be lifted from th< 

and either end of the 280 fl . lofl 

in less than five mimil e 

On the main floor of this barn is a rool 
cutting mat hine for p d for the 

crated by a 2 h.p. 

motor mounted on the ceiling and bell 

connected to the machine, the controller 

he wall b machine. 



172 



CEXERAL ELECTRIC REVIEW 




Motor Operated Hay Hoist and Controller 

In the dairy section is a vacuum pump 
operated by a 1' h.p. motor and supplying 
power for milking machines. A metallic 
vacuum pipe leading from the pump is 
permanently located around the outside of 
a double n >w of cow stanchions, with an outlet 
lor each pair of stalls controlled by a single 
valve. When ready for milking, ir is 

started and flexible tubes from the milking 
machines arc connected to tin- vacuum pipe 
outlets; soft rubber cups al the ei her 

flexible tubes connecting with the milking 
machine are th< 1 on the nipples of 

the cows, where they are securely held by the 
uniform pressure created by the vacuum. 

There are five of these machines used at 
Heart' Delighl farm, each machine milking 
two cows simultaneously. Thesuctii lied 

rmittently by an automatic valve on the 
milking machine; ami thus by alternate pres- 
sure and relaxation th< of hand milkingis 



obtained, with the added assurance 
of absolute cleanliness, since the 
machines are totally enclosed. The 
milk as it is withdrawn from the 
cow passes through a short glass 
tube in the top of the machine and 
is in this way made visible to the 
operator, who is thus enabled to 
stop the process at the proper time. 
The milk is then carried to a room 
located on the same floor and pro- 
vided with a motor driven separa- 
tor. After being tested it is passed 
; hri nigh the separator, the cream 1 ic- 
ing thence taken to the butter mak- 
ing section of the dairy building. 

A 1-i h.p. vertical shaft motor 
having an initial speed of 2(100 
revolutions per minute runs the 
separator. Upon its arrival in the 
dairy building the cream is depos- 
ited in a covered tank and is 
ripened before being piped to 
the churn. The churn is driven by 
a .'! h.p. motor, which is mounted 
directly on the churn frame and 
drives it and its auxiliaries through 
gears which are enclosed in a sheel 
iron casing to insure safety and 
cleaniness. 

The motor starting rheostat is 
mounted on the wall back of the 
churn, the solenoid of the rheostat 
being arranged that it can be short 
circuiting from the front of the 
churn, thus permitting the operator 
io stop the churn instantly, at a distance from 
the rheostat, by simply pressing a button. 

All the milking ami butter making proces- 
ses arc carried on by, or under the direct 
supervision of experts: this arrangement to- 
gether with the high grade cattle and scienti- 
fic feeding insuring the best quality of dairy 
products and a correspondingly good market. 
Near the dairy building is an ice making 
plant with a capacity of twenty tons every 
t went y -four hours. Motors arc utilized for dri- 
ving the pumps, although there is also a steam 
equipment for the purpose; this, however, is 
held only as a reserve. Two ammonia pumps 
arc driven through chair, drive by two 20 h.p. 
motors, and the brine circulation pumps 1 y 
two :\ h.p. motors, also through chain belts. 
This plant uses only spring water and 
furnishes ice for drinking purposes, for cold 
and for the shipment of products 
affected by changes in temperature. 



ELECTRICITY ON jTHE FARM 



L73 



A small centrifugal lift pump direct con 
nected to a 7\ h.p. motor is located in the 
ice machine building and elevates water 
to a nearby tower tank. This motor runs 
at L500 revolutions per min- 
ute, and as both the centri- 
fugal type of pump and the 
electric motor operate best 
at relatively high speeds, this 
unit is a particularly good 
example of a compact, high 
efficiency pumping set. If 
necessary, it can be equipped 
with device, which will auto- 
matically maintain a prede- 
termined water level in the 
tank. 

A substantial grist mil! is 
included among the farm 
buildings and the machinery 
in this is driven through 
counter shafting by mean 
of a 25 h.p. motor, housed 
in a separate building to 
eliminate the fire risk due to 
the presence of inflammable 
grain dust in the mill. Many 
modern grist mills, however, 
use motors which arc installed in the mill 
buildings, and the polyphase induction motor 
is peculiarly adapted for this service owing to 
the absence of a commutator; thus elimi- 



I taken out in the field in this way and 
used to drive a threshing machine, the 
nece :ary conductors being laid along the 
ground to supply the current. 





Butter Churn Operated by Direct Geared Motor 

Dating the potential danger from parking 
brushes. 

The grist mill motor is nol I on permanent 

foundations, but is mounted < I a iruek and 
can therefore be readily transported to oth r 
buildings for temporary or i y service. 



Milking with Vacuum Operated Milking Machines 



The use of portable mi >t i irs Ei ir field work on 
farms is becoming of increasing importance 
wherever electric current is available. A 

notable example of its possibilities was recent 
ly given in Germany, where two motors 

— , were used to pull plows .across a field 
by means of steel cables actuated by 
motor driven drums. Two portable 
motor driven outfits were located on 
Opposite sides of the field and mo ed 
forward as the plowing progressed. < >f 
course, this method of plowing would 
only be practicable under certain con 

ditions; but it illustrates the all-round 
adapabilitj of the elect ric motoi 01 
farm work. 

An item of growing importance at 
Heart's Delight farm is the production 

Oi hi .it Chopping and 

mixing machine . tor winch ait 
ven by a single I h.p. motor utiliz- 
ing an overhead counter haft . The 

,m tg are filled 1 

operated by hydraulic pn no and i oin 

■ d air, .and in this way two men 

maintain continuous production up to the 

city of th i quipmenl . 

The t wo I applied with rool 

CUtl ing na ine driven through belting by 



174 



GENERAL ELECTRIC REVIEW 




Two 20 H P. Motors Driving Ammonia Pumps in Ice-Making Plant 



motors of 1 ', and 2 h.p. capacity. The motors 
arc mounted on shelves and therefore occupy 
no space which could he otherwise utilized. 
One of the farm auxiliaries is a thoroughly 
equipped fish hatchery used for the pro- 
pagation of trout. A number of con- 
crete fish ponds, located at slightly 
different levels in order to maintain 
the necessary water motion, have been 

ructed, and the fish fond is pre- 

1 by a grinding machine, belt i 

d o a 2 h.p. motor. 
Everj farm occasionally requires 
carpentrj work, and the use of up-to- 
date w 1-working machinery will al- 
ways expedite such work and lessen the 
labor cost. The serviceability and 

>m\ of motor drive for wood 
working machinery has led to its ex- 
tended adoption in sawmills and other 
v l-working plants, and one of the 

t plants of the kind in the world — 
that of the Great Southern Lumber 
Companyal Bogalusa, La. is equipped 
with General Electric motors through- 
out. 

The utility fo the electric motor in 
the operation of woodworking machin- 
ery on the farm, for farm building I 



struction and repairs, and for repairing 
wagons, etc., is well demonstrated here, 
where the wood-working building eon- 
tains a 30 in. band saw and a wood 
surfacer, each driven by a 7^ h.p. 
motor. The band saw is directly con- 
nected to the driving shaft of its motor, 
while the wood surfacer is driven from 
a countershaft. There is in addition a 
wood planer, which is driven by a 5 h.p. 
motor, and a circular saw and a wood 
boring machine, also driven by a 5 h.p. 
motor. 

lit connection with this woodworking 
shop, there is a machine shop having a 
30 in. drill driven by a 2 h.p. motor 
ami an engine lathe driven by a .'! h.p. 
motor; both motors being mounted 
directly on the machines and 'driving 
them through gearing.) 

The blacksmith shop has not as yet 
been electrically equipped, but a motor 
driven centrifugal forge blower and a 
motor operated trip hammer will be 
installed there at an early date. 

While windmills arc used for pump- 
ing the water for some of the outlying 
buildings on the farm, there is also a 
.") h.p. induction motor installed in a pump 
house and direct connected to a triplex recip- 
rocating water pump. This is the only 
alternating current motor installed on the 
farm at present, but the further adoption 




Motor Driven Brine Circulation Pumps in Ice-Making Plant 



ELECTRICITY ON THE FARM 



I?.") 



of this type of motor is be 
ing considered in providing 
for the future extension of 
the electrical service, as it 
is the best form of motor 
for operations requiring a 
constant speed. 

In addition to the pre- 
sent equipment, motors will 
hereafter be utilized on this 
farm for shearing sheep. 
clipping horses and other 
similar work. 

Motor drive has been ex- 
tended to the housework, 
and there are installed in 
the laundry of the main 
house on the farm, known 
as "Heart's Delight Cut 
tage", a clothes washing 
machine driven by a 3h.p. 
motor a centrifugal dryer 
operated by a 2 h.p. ver- 
tical shaft motor, and a 
mangle driven by a 2 5 
h.p. motor direct con- 
nected. 





Grist Mill Machinery which is Driven by a 25 H. P. Motor Homed 
in a Separate Building 



View in Sausage-Making Department. Showing Meat Cutting. Mixing and Bone 
Grinding Machines 



Among the auxilian electrical de- 
vices at I he cottage are an electric 
piano, heating and cooking devices, 
and a motor driven ice cream freezer. 
Fan motors are also liberally pro- 
vided. 

Electricity on the farm not only 
permits the ready application of power 
to machinery located in widely si 
rated buildings, but insures I 
and must efficient lighting for both 
buildings and farm yards. 

At 1 1 earl's Delight Farm the buildings 
are .-ill light <'d with incandescent lamps, 
and in order i" insure absolul i 
they are enclo :ed in \ apor-proof en 
closing globes which lit into porce- 
lain bases, the wiring being all run 
through iron conduit. In the \ 
i he high effii ienc i if the flaming arc 
lamp for tin 1 lighting oi Lai 
has resulted in its adoption for the 
purpo i . and four lamps of this type 
are used, one ol them being installed 
on the top of the 134 ft, sti 
lower. At .in earl date, the light- 
ing system will be extended to the 
r< uil" a ! on the farm, and either 
luminous are or incandescent lamps 

will be ll 



176 



CEXERAL ELECTRIC REVIEW 




View in Laundry, Showing Motor-Driven Washing Machine and 
Centrifuguat Dryer 



embankments 

fully sodded. 
various farm 
underground 



which have been care- 

The wiring to the 

buildings is carried 

in conduits, and a- a 



consequenee there art- no unsightly 
effects produced by the various 
conductors which radiate from the 
farm power station. 

It is obvious from the foregoing 
that the adoption of electricity on the 
farm > a marked saving in the 

labor cos) of a greal variety of oper- 
ations and renders possible those 
economies in production which result 
from the elimination, either wholly or 
in part, of manual labor and the sub- 
stitution of mechanical devices which 
are highly efficient and easily oper- 
ated and controlled by the aver 
farm worker. 

It renders possible the adherence 
to a definite schedule of work- and 
therefore enables the modern farm to 
emulate the successes obtained in 
other industries by the most econom- 
ical use of that expensive commodity, 
modern labor. 






In accomplishing the electrification of this 
farm, every effort has been made to preserve 
the natural beauties of the farm lands. 
The concrete dams are smoothly finished 
and the penstocks covered by earth 



Heart's Delight Farm has had 
electric service for a period of about 
three years during which time it 
has been definitely proven that the 
electric motor can be applied with unqualified 
success to the operation of all machinery used 
in farm buildings. It constitutesa potent argu- 
ment for the general adoption of electricity 
on the farm. 










General View of Heart's Delight Farm 



HYPERBOLIC FUNCTIONS AND THEIR APPLICATION 
TO TRANSMISSION LINE PROBLEMS 

Part I 
By W. E. Mill ik 



177 



Introduction 

The discussion of transmission lines'has not, 
as a rule, considered lines much above 200 
miles in length. This being the case, ap- 
proximate methods have generally been used, 
as these possess all needful accuracy for lines 
not over 200 miles longoperaliti'j a ii() i 
or not more than nearly double this distance 
ai 25 cycles. When applied to greater dis- 
tances, however, these methods are not relia- 
ble,* and the following discussion of long dis- 
tance lines has therefore been prepared. These 
methods are equally applicable to short dis- 
tances, and in general arc as simple to handle 
as those usually employed. The results are 
obtained from the exact solution of the gen 
eral equations which solve the problem of 
transmission lines with distributed capacity 
and self induction and leakage, of which 
the last can appear either due to corona 
effect, t or to leakage at the insulators. 
The various constants required for the 
complete computation of any transmission 
line likely to be used for some time to come 
have been calculated, as well as the mathe- 
matical tables necessary for the work. The 
solution employed is that used by Kennel! y 
and involves the use of hyperbolic functions 
of the complex quantity. The use of the 
complex quantity was first introduced into 
this problem by Steinmetz, with a resulting 
simplification of the formula? and operations 
required for obtaining results. 

Applications of Formulae and Conditions Necessary 
for Determining Problem 

The determination of the power factor, 
voltage and current can be as readily made 
at any point of the line by this method as at 
the line terminals, a matter of considerable 
importance where another line is connected 
at some intermediate point. Further, except 
for changes in sign, the same formulae apply 
whether the terminal conditions are given for 
the generator or receiving end, so that it is a 
matter of indifference so far as the calculations 
are concerned at which end the volts, current 
or power factor are given. 

The calculations can easily be adapted to 
take care of eases where two of the terminal 
conditions are given for, >ay, the receiving 
end. and the other condition for the generator 
end. Actually, the method i not limited m 

•Sec Steinmetz "Transiint Phenomena" pa 

t Only true if voltage is practically I on n« the line' 



any way and can be used, if necessary, to 
soke cases where three < Lei trical conditions, 
such as volts, current, and power factor art: 
given at any point or points along the line, 
or where two power factors and a volta; • or 
current are given, or any combinations of 
these factors, provided that none of them is 
used more than twice and that only three- 
are given. 

Tables and Constants Calculated 

( Ine of the reasons why the hyperbolic- 
functions are not commonly known is due to 

lie absence of complete and readily available 
tables of their values. In transmission line 
problems, where hyperbolic functions of the 
complex quantity are used, the tables so far 
published do not give the values of the 
functions at sufficiently close intervals to 
allow of either ready or accurate interpola- 
tion. A sufficiently complete set of tables has 
therefore been computed which give the 
values of these functions at intervals which 
allow interpolation to be made by inspection 
for any value of the function which lies 
between those tabulated. The tables have 
been very carefully calculated and through 
the greater part of their range can be relied 
upon for an accuracy of one half to one- 
quarter per cent. They will be published in 
the next issue of the Review, together with 
a tabli of the constants required for calculat- 
ing transmission line problems involving 
their geometrical properties, i.e., capacity 
and self induction, at frequencies of 25 and 60 
cycles. 

The latter constants arc calculated for 
three-phase transmission with the three 

win placed at the corners of an equilateral 
triangle, and for the wires equally spaced and 
lying in a plane, provided a sufficieni number ol 
transpositions has been made in I he lat t crease 
toobiaina balanced system. The constants 
include lines using wires from No. 2 B.iVS. to 
_'."in, ill ill i m . mills, and are calculated for the 
pacings, 6 ft., 8 ft., in ft., and 12ft. 
As the values of th< constan do lot change 
quickly with the spacing, the proper constant 
can be at once determined by Lnspe 
for any spacing lying between tho 
mined. The capacity and self indu 

< I in these 'its are taken be 

t ween line and nentr.il, SO that the voltagi 
relating to them is that between line and 
neutral and m multiplied by \/3 to 

obtain the line voltagi 



7^ 



GENERAL ELECTRIC REVIEW 



Operations Required and Speed of Calculations 
Possible 

By the aid of these tables and constants, 
the calculation of the power factor, amperes 
and volts at the generator end of the trans- 
mission line of any length up to nearly 500 
miles long for 60 cycles, and nearly 900 miles 
long for 2o cycles, can be performed with a 
little practice in about a quarter of an hour, 
when volts, amperes and power factor arc 
given at the receiving end, or vice versa. 
From these results, the transmission eff- 
ciency can be at once obtained for the given 
load, and the line regulation can be deter- 
mined by a calculation for no-load conditions 
by means of a simple multiplication. The 
electrical conditions at any point of the 
transmission line can also be as easily and 
quickly computed. In fact, after looking 
up the proper constants to employ and the 
values of the hyperbolic functions, as given 
in the tables, tin- whole problem, so far as 
results ; es itself into two 

multiplications and one addition for obtaining 
either volts or amperes at any point, and two 
divisions for obtaining the power 
although a tabl o cosines is necessary for 
the latter. 

Curves Illustrating Electrical Conditions Along the 
Line 

To show how the electrical characteristics 
vary from point to point in a long trans- 
mission line, curves have been plotted lor a 
transmission line Kin miles long, using three 
0000 stranded hard drawi r wires, with 

a spacing of ten feet between wires, operating 
at a frequency of 60 cycles. These curves 
and the ones mentioned below, will be 
published in the next issue of the Rivn \\. 
where this side of the matter will be more 
fully discussed. They include curves showing 
the variations of volts, amperes, and power 
factor along the line, under various conditions 
at the receiving r factor and 

load, the volts at this end being assui 
constanl and 60,000 volts. ,„• 104,000 volts 
between wire-. Curves illustrating a method 
for determining what power factor at the 
receiving end gives maximum transmission 
effii i .m\ given load delivered. Curves 

illustrating the corona effect along a line 
l'iiii miles in length operating at 25 cycles, 
using No. 1 wire with a of S ft . 

a voltage of iKl.tKKi volts between wires. 
The power wasted in capacity current and 
owing t<> corona an itely plotted for 

each point of the line. The corona constant 



used in these calculations was computed from 
results obtained on a 50 mile line, operating 
at a line voltage of 110,000 volts. This line 
is, electrically similar to the one taken for 
illustration, so that it is believed that the 
corona effect calculated cannot be far from 
the true value. 

Lastly, the hyperbolic method has been 
applied to a telephone line consisting of two 
Xo. (i B.&S. wires twelve inches apart and 
lniiii miles in length, the frequency being 
taken as 1000 cycles per second, and the 
pi nver factor of the receiving apparatus being 
assumed to be .5 lagging. The voltage require 
ed for the receiving' instrument has been taken 

2 volts. and the current as .5 milli-amperi 
The hyperbolic functions in this case had to 
be specially calculated, since the tables do 
not cover the range necessary. Curves have 
•>. plotted giving the variation of the 
maximum value, as well as the instantaneous 
values of the current and volts at every point 
of the hue. This problem illustrates the 
shift of phase of current and volts along the 
line and the finite velocity of electric wave 
propagation much more forcibly than any 
problem relating to commercial transmission 
lines, and it was chosen for this reason. 

Introduction to Mathematical Portion 

The majority "f engineers, unfortunately, 
arc not familiar with hyperbolic functions, 
and the complex quantity has not received 
the attention it has deserved of the electrical 
fraternity. The hyperbolic functions are 
extremely simple and arc as easily under- 

1 as the circular functions, sine, cosine, 

etc.; while the complex quantity is one of the 
greatest labor and thinking saving methods 
of treatment devised, and carries its physical 
meaning through all the mathematical oper- 
ations to which it may be subjected. As the 
understanding of the following cut 

depends on these matters being apprecia 
the following short discussion is given, 
which may help to elucidate the meanings of 
these quantities and the laws governing 
them. 

Hyperbolic Functions 

The hyperbolic functions, as their name 
implies, can be derived from the hyperbola 

in a manner similar to that employed in the 
derivation of the circular functions, sine, 
cosine, etc. The following discussion illus- 
trate- the close antilogy existing between the 
two methods.* 



► See Osborne's "Integral Calculus, p., 



LONG DISTANCE TRANSMISSION LINE PROBLEMS 



Consider the circle x t +y i = a t 
Let the angle POA =0 and let thi sectorial 
POA =u 

Then x = a cos $ and y= a .sin 



W hili- u = —5- or e = -j 
2 a- 



Hence, OM- 



11 



ami — = 



e — f 



(7; 



Hem e, OM =x=a < <wA 

<r 

2« 

and /'.l/ = v=u s»"»ti t , which arc exactly simila 



and P M = v =1/ stn 

J n- 



(2) 



That is to say, the length O.U. or x, divided by 
the radius or distance from the center of the 1 ircle 
to the circular boundary, is equal to the cosine o( 
the ratio of twice the sectorial area to the constant 

area of the square erected on the radius. 'Pin lengl h 

I'M 

— — is equal to a similar function involving the 

sine in place of the cosine. 

If the above definition is applied to the 

rectangular hyperbola, the values of the 

hyperbolic sines and cosines, or sinh and cosh, 

as they are usually denoted, can be as readily 

obtained as follows: 

Let () be the center of .> rectangular hyperbola, 
il which the are is PA. 

Then the equation of this hyperbi ila 1 eferred to its 
center is x- — y- =a-. 

The sectorial area u \~ equal to tin- shaded 
of Fig. 2. and equal to the area of the triangle 
POM — area PA M . which is equal to 

*y C x a j 1 x +y 

~2~ ) ydx = -• *y ' ■ *y + ~% l0R „ 



a- x+y 

■ 2 ■'"" a 



Whence 



and 



.v+y 






14) 



(5) 





f: 8 . 2 



expressions as those obtained for thi circular 

Hi 



functions. If 9=angle POA then tan 



liinh -5 
<;- 

The values of sinh a and cot h x can thus be obtain- 
ed in terms of tin ins, i.e. 

sinh x = ., anil cosh x = 

It will be observed thai foi large values of x, the 
qual, in' ] i!i..i ; ' 
sinh x is equal to cosh 1 when x is large, when 
tnnh x = 1. 

The analog ii >ns sin x and cos x 

lull. '"■ 



2 



and • 



2/ 



I0)ai 



when- j is imaginary and equal N I. whi 

1 .'■• v do in >i involve 

[inarie fhi presence ol ii 

nential 1 for sin and 1 os render 1 1 

periodic in value; ol these imaginaries 

in the straight hyperbolii functions make 1 
11. a, pi 1 iodii The 1 ompl •■. li s have, '. 

■en later. 
ubtracting (8) and 9 '■wing 



M /J 



sinh x = ■ 






Fig I 

e by definition similar to that given fo 
circular fun. tions in the case of th 



+ e< 



•=cosh 



6 






1 , 






from which the valu 
calcul 

1 li. ,1 Mn ion and >l tin 

Mil y 
and cos i 1 os y [ tin >■ tin 
formulae being readil 



isi) 



GENERAL ELECTRIC REVIEW 



the properties of the circle. The following formula- 
can be deduced for the hyperbolic functions from 
the geometrical properties of the hyperbola in a 
similar manner. 

sin h(x+_y) =sinh x cosh y + cosh x sink y (\4) 
cosh (x+_y) =cosh x cosh y±_sinh x sinh y (15) 
By changing x into — .v in 8 and 9, it follows that 
cosh x=cosh(—x) and sinh x= — sinh(-x) 
also cosh o = l, sinh o=o, cosh fob'='6o, sinh s. = oe 
hence, tank x = 1 and tanh o=o 




By the addition and subtraction formula-, 14 and 
15, the following relations are seen to exist: 
sinh 2x=2sinhx coshx 
cosh 2.v = cos-hx + si»h' : x 
cns-h x — sin'-h x = l, etc. 
Compare sin2x = '2si»xcosx 
Cos 2x = cos'x — sin'x 
Cos'x+sin'x = 1 
From Sand 9, we have also 

d sinh x <•' + e~ x 

— s =cos h x 



dx 

d cosh x 
and 

Therefore 
d-sinh X 

dx' 
d-cosh x 



h x 



and 



dx' 



= si»h x 



■■ i osh 



That is to say, the hyperbolic functions 
repeal th in two differentiations, 

which may be regarded as the mathematical 
reason why they appear in the solution of the 
equations relating to transmission lines. 

It i til from 1 he ab >\ e how closelj 

the formulae of the hyperbolic functions 
follow those of the circular, and how readily 
are obtained. For further information 
on these functions and on the hyperbolic 
complex, sec McMahon "Hyperbolic Func- 
tions." 

Complex Quantity 

As is well known, all directed ph 
quantities can be represented vcctorially, 
the scalar part or length of the vector rep- 
resenting the magnitude of the quantity, and 
the direction of the vector representing the 
direction of the quantity. Such a vector can 
be resolved into two vectors, at right angles 
to one another. The simplest notation to 



employ in such cases, to differentiate be- 
tween the horizontal and vertical component, 
is to prefix a symbol in front of the vertical 
component. This symbol, in electrical science 
is usually called j, and means that the vector 
in front of which it stands must be added 
vectorially to the horizontal component and 
not algebraically. 

Thus if b represents a horizontal force, and 
c a vertical force acting at the same point on 
a body, the resultant of the force will be 
denoted by b+jc, the magnitude of the 
re sultan t being by the parallelogram of forces 
\/6 2 +c 2 , making an angle with the horizontal 



component 6 = la 



- (0 



This at once shows 



that in order to get the magnitude of the 
vector, of which the two rectangular com- 
ponents are given in the form of b+jc, tin- 
square of b must be added to the square of c, 
and the square root extracted of their sum, 
and that the angle the horizontal component 
makes with the vector is given by the equation 

tan 0= —. Vectors thus resolved into com- 
b 

ponont vectors at right angles to one another 

are very easily operated, when the meaning of 

j is appreciated, and the sum of the component 

vectors is called the complex quantity. 

In order to discover the meaning which 

should be assigned to the symbol j the 

following case is taken, let P represent a 

force acting along a constant direction OP 

through a length / lying in the direction 

of OP (see Figs. 3 and 4). Then the work 

done by the force is equal to PL Now 

suppose that the force P is resolved into two 




components, b+jc, and the length similarly 
into two components y+jz, then the product 
so far as magnitude is concerned 

(b+jc) (y+jz) 
must equal I p. This pro duct equals (by +j'zc) + 
j{bz+yc). If J is equal to y/ — 1, the above expression 
becomes (by — zc) +j(hz+yc), and the magnitude of 
thi s vec to r is given by \/(by — zc) 2 + (bz+yc)' — 
y/b'+c'x/yi+z* which is equal to IP. iHcnce, the 
value given for j yields acorrect result. 



ELEMENTS OF TRANSFORMER CONSTRUCTION 



is I 



Better illustrations perhaps could be obtain- 
ed from electrical engineering, because work is 
notadirectioned quantity, but the idea is so fa- 
miliar that the foregoing illustration waschosen. 

Currents and volts can be resolved into two 
components at right angles to one another 
in a similar manner. And, since inductive 
reactance and dielectric susccptance are 
proportional to the rate of change of current 
and vi ills with time respectively, they can be 



regarded as at right an o the resistance 

ami conductance in the functions impedance 
and admittance. Thus, the impedance and 
admittance can be represented as r+jx ami 
g+jK respectively where r is resistance, * the 
reactance, g the conductance, and K the 
susceptance. These quantities are, of > o 
scalars, but the method applies to anj 
quantities which can be resolved into two 
directions at right angles to one another. 



THE ELEMENTS OF TRANSFORMER CONSTRUCTION 

Part I 
By W. A. Hall 



In electrical work, the term "transformer" 
is used to denote a certain class of apparatus 
which embraces a great variety of devices, 
each possessing a certain given inherent 
characteristic of marked simplicity. 

Probably the simplest geometrical con- 
ception of a transformer is that suggested by 
three links of a chain, in which the middle one 
represents the magnetic and the other two 
the electric circuits. In constructing this 
device, however, the designer is immediately 
confronted with certain conditions which 
materially modify his elementary figure. 

The best materials commercially available 
for these circuits (steel and copper, respect - 
ively), are far from the theoretically perfect 
in that their highest efficiency is much below 
100 per cent.; or, in other words, each offers 
a certain resistance to the transmission of 
electrical forces that results in an energy 
loss, operating against the efficiency of the 




Fig. 1 

transformer. The resistance in the copper 
directly with the length and 
inversely with the cross section of the con- 
ductor, while the loss varies directly with the 
resistance and as the square of the current 
carried by the conductor. The resistance 
to the passage of magnetic fori i ough the 
iron circuit usuallv termed "reluctance," 



Fig 



also varies directly with the length and 
inversely with the cross section of the core. 
The relation of loss to reluctance, how 
is somewhat more complicated, owing to the 
fact that while the specific resistance of 
commercial copper wire is practically uni- 
form, the specific reluctance of commercial 
steel varies widely. Eliminating this variable, 
we still find that any grade of steel of given 
dimensions has a different reluctance for 
value of magnetic force, that i ., the reluctance 
varies in a fixed relation with what is termed 
the magnetic density. Therefore, while it is 
not convenient, generally speaking, to express 
the loss in a magnetic circuit ("core loss") 
in terms of reluctance, it may lie safely taken 
as somewhat greater than the first pi 
relation, or the relation which exists between 
r loss and resistance in the copper 
members of the transformer. 

Prom the foregoing it is evident that a 
minimum loss in each mem- 
ber results from thai circuit 
which has minimum len 
and maximum cross-section. 
It is equally obvious that these 
conditions are conflicting in 
the primitive linkage, which 
fad renders this arrangement 
open to improvement, while 
r consideration make it 
in exact form practically pro- 
hibitive. It is furthei 
ed thai | ia e li • I in one of the 
nts by reason of the greater length im- 

: i- 1 ed upon theol her , caUSi I herein botl 

of elect i ii al effici" qi i ial, repr< 

ing a donl ile u a te, I lore, 

the space fa< ratio of net 

■ e material to ace oc< upied, 

maximum in b( id ci ipper 
< ircuits. 



182 



CEXERAL ELECTRIC REVIEW 



Opposed to this are considerations of equal 
or greater importance. In order to increase 
the resistance in the path of the wasteful eddy 
currents within the core, this member is 
built up of laminations or punchings of sheet 
steel, varying in thickness in commercial 




Fig 3 



Fig. 4 



transformers from It to 25 mils., to which 
is added on each side a coating of some 
insulating material that increases the thick- 
ness of the sheet by approximately another 
mil. This insulation, together with the loss 
of space incident to building up into a core, 
causes a loss of from 5 to 20 per cent., or in 
other words produces a space factor varying 
from 95 to St) per cent. 

In the copper circuit it is necessary to 
insulate each turn from all other turns thereof, 
and from all other parts of the transformer. 
Since the potential accumulates along the 
conductor, it follows that the amount of 
insulation required between adjacent turns of a 
coil is relatively small . that between sections 
of acoil being somewhat greater, while that 
between other parts and the coil is consider- 
able. The entire amount of ;pace given up to 
this most essential feature is even more than 
that occupied by the copper, and therefore 
the space factor of the copper circuits in the 
average transformer is lowered to a figure 
well under ."ill per cent. Thus far. the dis- 
cussion aims to show the value of the sp; 
encompassed by both the magnetic and 
current elements of the transformer. 

The engineer is next confronted with the 
; in iblem of conserving this space by designing 
in the form of regular geometrical figures, 
which will hes: accomplish the result in a 
manner consistent with economical manu- 
facture. For reasons already referred to 
cores must lie laminated, and moreover, 
in such a manner that they can be readily 



linked with the copper circuits. The preven- 
tion of waste of material during manufacture, 
which requires straight line punchings that 
interlock, at once determines the rectangle as 
the form of the magnetic circuit for nearly all 
commercial transformers; a conclusion which 
is strengthened by the fact that this figure is 
also best adapted to the formation of the coil 
sections which it encloses. These and other 
considerations have led to the development of 
three general types, upon one of which nearly 
every commercial transformer of any con- 
siderable capacity is constructed. These types 
are shown in Figs. 2, 3 and 4, numbered respec- 
tively in the order of their commercial origin. 

The design in Fig. 3 was employed ex- 
clusively from the beginning of transformer 
manufacture in this country in L885, until 
1895. It consists essentially of rectangular 
coils, wound upon a rectangular form. The 
core, instead of being a single link as in our 
elementary conception of the transformer, 
has a double magnetic circuit. The portion 
within the coil was considered the core 
proper, and at a very early date came to be 
known as such. The remainder of the iron 
circuit was in a similar manner identified as 
the "shell." Since the coil is principally 
within the iron, it follows that one char- 
acteristic of this type is a relatively large 
amount of iron and a small amount of copper, 
and consequently, a small cross-section of 
the latter. For a given voltage then, this 
necessarily means few turns, which fact, for a 
given core loss, demands a large cross-section 
of the magnetic circuit. This in turn results 
in a long mean length of copper and short 
mean length of magnetic circuit. 

'fhe design shown in Fig. 4 was introduced 
commercially in this country about L895. 
Fundamentally, it is directly the reverse of that 
of Fig. '■). in that the coils are, in general, 
disposed externally. 

These two types of transformers have been 
named according to the arrangment of the 
iron with respect to the winding. Since that 
portion of the core which is called the shell is 
a prominent feature of the design shown in 
Fig. 1. this type has become known as the shell 
type. In contradistinction, the design shown 
in Fig. 2. in which the greater part of the iron 
forms the core proper, is called the coret pc. 

'fhe core type has relatively a lighter core 
of less cross-section and greater mean 
length, while the copper is relatively In 
and of larger cross-section and is composed of 
a greater number of turns of less mean 



ELEMENTS OF TRANSFORMER CONSTRUCTION 



183 



length. Since the introduction of the core 
type approximately L5 years ago, the design- 
ing engineer, manufacturer, salesman and 
operator have engaged in an endless and 
verbose struggle to demonstrate the super- 
iority of that particular type in which each was 
interested. If, in the face of this controversy, 
the author may venture an opinion, it is to 
saythateach type has its comparative advan- 
tages and disadvantages, depending upon the 
particular use for which it isintended. In tact, 
si line manufacturers make both types for the 
same or different service, and in this manner 
have done much to eliminate artificial differ- 
ences and make the two more nearly alike. 

The shell type, having a large ratio of 
cross-section of core to coil, is at once superior 
to the core-type with its opposite character- 
istics, when the service demands high duty 
from core and moderate requirements from 
coils. The core-type, with its large ratio of 
coil cross-section to length, likewise possesses 
an advantage in those instances where 
conditions are exacting with regard to wind- 
ings. Hence we find the shell type particu- 
larly adapted to transformers of moderate 
voltage, requiring few turns and little insul- 
ation, large currents (easily provided for by 
heavy conductor in its few turns), low- 
frequency and consequently heavy flux; 
while the core-type, with its ample winding 
space, lends itself more readily to the higher 
potentials which require many turns and much 
forinsulation, smaller currents and lighter 
wires for the many turns, and higher frequencies 
with low magnetic densities. Hence it follows 
that the former is essentially a high capacity 
and the latter a low capacity transformer, 
which fact accounts for the practice of the 
manufacturer who builds a core-type for his 
small transformers and those of exceptionally 
high voltage, and in lar.'.i- power transfor- 
mers upon "shell-type" lines. 

Now as we compare without prejudice the 
two types before us, we will in general con- 
clude that, because of thi mean 
length of the core of the shell-type and the 

of ill- core-type, these elements po 
advantages over corresponding elements oi 
opposite typi \ immediately 

the possibility of a marked gain could aux- 
in' devised whereb 
advantage mighl be a imbined. T 
the solution of this problem, Ie1 us briefly 
return to our fir: : of the bran 

former; viz:, the three links. In Fig. 1 we 
have a single magnetic circuit and double 



copper circuit , hence a core-type I ran ifo 
In Fig. l' we have a double magnetic circuit 
linking a single copper circuit, or a form of 
hell-type transformer. Now, if the 
al links represent coils or cores oi ;ub 
stantial magnitude of cross-section, the 
length oi the external member may lie mater- 
ially le :i ned by distributing them about the 
periphery of the eni lo ed member. 

This development will result respectively 
in Figs. ."> and <i, which may he considered to 
fairly well represent the ideal transformer 
of highest efficiency, where each element is in 




Fig. 5 

the form of a circle, and hence has a minimum 
length for unit area enclosed. There are 
many obstacles between this design and its 
commercial use, such as lack of good mech- 
anical characteristics, difficulty of insulation, 
inabilitj to properly dissipate heat generated 
within the inner member, and excessive ! o 
of manufacture. 

The problem then narrows down to thai of 
combining the advantage m points of the two 
types and extending the development a 
as possible toward the de ign of the theori 
cally best. To that end there v 
upon the market in 1905 the design hown in 
Fig. 7, which, by subsequenl adoption as the 
standard type for .mall transformers of the 
two largest manufacturers in this country, 

probabl) the majorit; 
trar.si- 'rim rs lade 1 herein. 

Thai we may derive a proper co 
of this transformer, let i 
! modified by placing all of its wind- 

on one 1 ' . for 

equal i 0ft ii ''is step has been at tended 

; addil ion in co I of material, becau ;e ol 
the lai ■ opper circuit. 



184 



GENERAL ELECTRIC REVIEW 



Now divide the iron circuit into two equal 
parts and rotate one through 180 degrees 
when we have Fig. 3, in which it should be 
noted that the width of laminations outside 
the coil has been reduced by one-half while 
the full cross-section has been maintained and 
the mean length materially reduced, thus 




Fig. 6 

gaining simultaneously in cost of material 
and iron energy loss. Consequently, to 
restore the original efficiency, the whole 
transformer may be reduced, making a 
double saving in cost. 

Consider now a second division whereby 
the iron in each of the two branches is split 
and one-half rotated !i() degrees, thus develop- 
ing Fig. 7. in which the width of iron is now 
one-half of that in Fig. ;'>. or one-fourth of that 
in Fig. 8, and the mean length of the magnetic 
circuit SO far shortened thai there results a 
very great saving in the cost of material for a 
given efficiency, or conversely, a greatly 
improved transformer for the same cost. 
Obviously, this process of division might be 
extended indefinitely until We arrived at an 
approximation to the ideal transformer. 
However, a little thought will disclose the 
fact thai there is a problem involved in thus 
dividing the center leg without loss of space 
factors, maintaining at the same time a prac- 
tical manufacturing proposition. In con- 
sideration of these fad ther with a 
number of others, such as coil radiating 
surface, oil channels, leads, cosl of labor, etc., 
it appears that this type as shown approaches 
as nearly as practicable to the ideal trans- 
former. 

It is at once apparenl thai thi ! new type, 
which is called the distributed core type, 
combines certain characteristics of the other 
two. As we have seen, the efficiency of the 



shell type demands small coil space and low 
mean length of magnetic circuit. Hence 
the opening in the core, or the window as it is 
frequently termed, is relatively short and 
broad; that is, it approaches a square. 
Consequently, it has been found profitable to 
make the coils narrow and deep, or of the 
so-called "pan-cake" type. On the other 
hand, for obvious reasons, the coils of the 
core type have become long and thin, or of the 
cylindrical type. Thus these features of 
construction have become to be regarded as 
characteristic of the respective types. 

It is the marked increase in the mean 
length of the magnetic circuit of Fig. 7 that 
enables the designer to lengthen the core o\ 
Fig. 3 so as to employ the cylindrical coils 
of short mean length — an advantage which is 
increased by the special construction of the 
core and which has become to he chart 
istic of this new type. Recognizing the fact 
that but approximately a third of the mean 
Length of the magnetic circuit is within the 
winding, this portion has been deliberately 
shrunk in cross-section and the loss incri 
therein, while the cross-section of that porti< in 
of the magnetic circuit outside of the coils, 
having twice the length, is corresponding!) 
enlarged to compensate therefor. There 
thus results the design which combines with 
the advantages of the core-type coil con- 
struction those of the shell-type core, though 
much improved. 

Let us now consider the practical appli- 
cation of these types. The comm 




llMflPP 



Fig. 7 

transformer is susceptible of division into 
four principal classes, each comprising a 
Lie. iter or less number of components, as 
follows: 

I. Multiple or Constant Potential: Rec- 
eiving an impressed electromotive force of 



ELEMENTS OF TRANSFORMER CONSTRUCTION 



185 



fixed value and delivering upon the secondary 
lines regardless of load, a voltage hearing a 
fixed ratio to that of the primary. 

II. Series Transformer: Connected in sei ii 
with the line, as the name implies, and hence 
receiving a current of a value depending 
upon the load therein; possessing the function 
of delivering to the secondary a current the 
value of which bears a fixed ratio to that 
impressed upon the primary. 

III. Constant Current: In effect, a com- 
bination of I and II, designed to receive a 
constant voltage and to deliver a fixed and 
constant current to the secondary. 

IV. Variable Ratio: Receiving a constant 
voltage and delivering a voltage varied at 
will, or receiving a varying primary voltage 
and converting it into a fixed predetermined 
secondary voltage. 

By far the greatest in importance is group 
I, in that it comprises the standard lini 
lighting transformers, testing transformers, 
all transmission and power transformers. 
as well as a host of miscellaneous modifi- 
cations for an almost infinite variety of 




Fig. 8 

purposes. Of these, undoubtedly the most 
familiar is the so-called lighting trail 
former, generally hung upon the cross 
of a pole in the street and receiving a vol 
of from 1100 to 2400, 10 to 60 cycles, and 
delivering from 1 in to 240 volts on secondarj 
lines carried into the building . More than 
half the value of the entire it, 
output in this count r\ COD 

ise of the fact thai the primary vol 
is dangerous to life, and the sei ondai circuit 

into almo :1 actual contact with n 
tudes of people, i1 is obviously oi paramounl 
importance that the secondary should be 



thoroughly and carefully insulated, while 
the large number of these transformers 
employed demands that attention be given 
to the important question of efficiency; both, 
together with other characteristics, giving 
the design, manufacture and sale of this 
dev ice great prominence. 




Fig 9 

Reference has been made to the fad that 
all three types described have been employed 
for this service and that the distributed core 
type has practically superseded the other t wo, 
although the latter is still manufactured 
by sonic companies. The most convenient 
form of punchings devised for this core are 
"L" shaped, and arc readily cut from the 
I 1>\ shearing dies in such a manner 
as to result in a comparatively small waste, 
at the same time permitting the dies to be 
operated at very high speed. As this 
of punching is particularly well adapted 
to the construction of the transformer, it 
is fairly economical. 

The punchings are built up by pairs into 
four sections which, when locked toge 
form a square center of solid iron with four 
branches at each end containing half the 
amounl of iron in the central core i I 
standing). This arrangement provides a nat- 
ural Spool-shapi d de ign, around the middle 
leg of which the coils are wound when it 
is placed in a winding lathe designed to 
properly hold it. This done, the ma] 
circuit is completed by interweaving the 
lamination of the four outside legs with those 

of the end branches. The lami i of the 

are secured by steel clamp placed al 
md bottom, which in turn are retained 
by straps of the san extending 

abOA c the top clamp and support- 
in;' the connection board to which are carried 
oil leads. The transformer is 
ted to a vacuum and filling pn 
after which the construction is finished bj 
: in;/ flexible insulated cables to the 
and a i mbling the transfi 
w ithin ii 



186 



GENERAL ELECTRIC REVIEW 



KEY FOR THE COMPLETE CALCULATION OF A TRANSMISSION LINE 

Part VII 
By Milton W. Franklin 



Given: 

(a) Kilowatts load 

(b) Length of line 
Power factor of load 

I Frequency 

(e) Number of pha 

(f) Estimated cost of power per kw. year 
( 'dsi of conductor per lb. 

(h) Interest rale Oil line investment. 

To Be Determined: 

(1) Voltage (see page 447, Vol. XII 

No. ini 

(2) Choice of conductor (see page 276, 

Vol. XII No. 6) 

(3) Most economic loss (see page 139, 

Vol. XIII No 
I Cross-sectional area of conductor 

equations c, e, g, i, page 140, 

Vol. XIII No. 3) 
a Bounds of conductor (equation •'!, 

page 139, Vol. XIII No. 3) 
b-Total cost of conductor 
c-Interest on line investment 
6) Resistance of line (equation 6, page 

139, Vol. XIII Xo. 3) 
a Skin effect (sec page 150, Vol. XII 

No. Hi) 
b-Recalculation of loss for cable sel- 
ected (equation /, page 141, Vol. 

XIII No 

(7) a-Kilowatts loss on line 
b-Kilowatts delivered (generated) 

C— Kilovoll amperes delivered (gener- 
ated 

(8) Line spacing of conductors (see 

table, page I 19, Vol. XII No. 10) 
a-Capacitv (sec table) 
b ( ' current (sec table) 

c-Self induction (see table) 
d Inductive reactance (see table) 
Natural period of line -see page 117. 
Vol. XII Xo. in, 
I 10) Voltage and current at generating 

end (under full load conditio 
(11) Regulation of line (unity power 

factor) 
( lL'i Summary of results 

The use of the key may best be illustrated 
!>•■ means of a worked example. 



Example- 

Proposition : 

To transmit 40,000 kw. (power at generator 

Length of line, 100 miles 
Frequency. 61 1 
Xumbcr of phases, 3 
Power fa. 1 .85 

Given: 

a. Kilowatts load. 40.000 

b. Length of line, 100 miles 
i . Power factor of load .85 

d. Frequency. 60 cycles 

e. Three-phase 

f. Estimated cost of power per kw. year S 10.00 

g. Cost of conductor per lb. — copper $.15 

— aluminum $.38 
h. Interest rate on line investment 5 per cent. 

Sm.e 20.00(1 kw. is the maximum load that can be 
economically transmitted ever a single line we shall 
ime two parallel lines of 20,000 kw. capacity, 
and consider each individually. 

The order of solution as outlined on page 139, 
V.,1. XIII No. 3. will be followed: 

1. Voltage receiver end 1 in I. IK III volts. 

2. Choice of conductor: Aluminum $.38 per lb. 
Copper $.15 per lb. 

From curve (see page 276, Vol. XII Xo. 01 it can 
be seen that copper will prove the eheapei con- 
ductor, aluminum will cost 18 per cent, more for 
the same percentage power loss on the line. 

Hard drawn copper wire is ehosen for tin 

ductor 

3 Mo i economic loss: See page 1411, Vol. XIII 
\i i. :;. liquations (/) and 

VSK 
I cE R *+3 K 
4000 pciKxKtL* 
cos'-e 
The values of the constants for this particular 

given below: 
P=pOWer at generating end. 20.000 kw. 

c= estimated cost of power per kw. year, $10.00 
E R = receiver voltage. 100,000 

L = length of line in miles, 100 

8=power factor of load. ,85 

c =cost of conductor per lb. $.15 

p = interest rate .05 
A'i = resistance of condui tor per mil mile 56,700 
k -weight oi ■ mil mile, lbs.. .0161 

From formula (4 < page 450, Vol. Xll No. 10. we have 
Ri = R . y 
R„ =55,810 I 6 1.016 urve, page 1 19, 

Vol. XII No. 10 

R« = 55,810X1.016 E =K, 

Substituting the values of the varii intsin 

the equation for A' we have 

A' = 4000 X .05 X . 1 •"< X 50,700 X .0 10 1 X 1 1 » l« 
- 



KEY FOR THE COMPLETE CALCULATION OF A TRANSMISSION LINE L87 



and 



=379,040,000 

3X37904X10* 



V 



= .053 



,4 X 10 X 10 10 +3 X37904 X 10* 

Thus we derive a value of 5.3 per cent, for the most 
economic loss, and hence can calculate the size of 
conductor = S. 

4. Cross sectional area of conductor [equation (g) 
page 140, Vol. XIII No. 3]. 
1000(1 -.v) 2 PA",L 

E R 2 cos-6 x 
100 0(1 -.053)'X20,OOOX56700X100 
iu 10 x..s5-x.o;.:; 
5 = 265,500 circular mils. 

But the nearest size standard cable is 250,000 
circular mils. This size cable (stranded cable) is 
adopted, and all the following computations ba led 
upon that size. This will alter our value of .v as 
found under economic loss, hence a new value .v, 
must be calculated, as given under (6 b of (his 
problem). 



5 = 



5 = - 



_(2a + l)± V 4« + l 

To 

In this case R, =22.86 

= 22 SO X 20.000 X I 

HI" 1 ■ s.V 

. = (1.1266) ±\ 1.2532 = 
A ' .1266 



0633 



0561 



The economic loss for this particular ca 
5.61 per cent. 

7-0. Kilowatts loss on line (Rl- loss) 
Kilowatts loss on line = /'A', 

20.000X.0561 =1122 kw. 

b. Kilowatts delivered at 100, volts, cos e 

.85 

20,000- 1122 = 18,878 kw. 

c. Kilovolt amps, delivered receiving 

ISS: ^.' SS : S k.v.a 

cos 9 .85 



I 




X. 



zr ? =&J - 9 



° §=/9.77 M \Ai C §=/9.77 6 C \\ 



T " 4=65.9 

2 C < 



I 




Fig. 15 



56700X100 nn . a , 
LT.O.OOO- =22-68 ohms. 



b-a. Pounds of conductor [equation (3) page 139, 
Vol. XIII No. 3] 
Pounds of conductor =3LKtS 
Lbs =3 X 100 X. 0161 X250.000 = 1,207,500 

b. Cost of conductor ($.15 per lb.) $.15 X 

1,207,500 =$181,125. 
This cost is for one line transmitting 20,000 kw. 

c. Interest on line investment (conductor only) 

per annum $181,125 X.05 =$9,056.25 
6. Resistance of line (single wire). Eq. (6) page 
139, Vol. XIII No. 3 

R ~ S 

The per cent, increase in resistance for 60 cycles 
(see Skin Effect page 451, Vol. XII No. 10) equals 
0.8 per cent, for the size cable adopted. 

This is an increase of 0.8 per cent, in the resistance 
hence the resistance per wire will I 12.68 < 1.008 
J2.86 ohms. 
b. Having the resistance of our cable v. 
Don in position to recalculate the I 150,000 

i in i lar mil i able, this being slight! I from 

, momii 1" la ls< '1' ulated urn li i 3) due to the 
fact of choosing ;i 250,000 circular mil cabli 
posed to a 265,500 circular mil cable as given by 
formula. Sec page 140, Vol. XIII No. 3 

1000 R,f> = .v, 1 i Ri 

E R *cos*e I c, 



, n k.v.a. 

a. Receiver current 

\ ■■'> Br 

1 28.2 amps. 



22,20(1 
\ .: ■ mo, (Kin 



8. Line spacing of conductors. (Tabli 
Vol. XII No. 10. 114 in. line spacing. 

a. Capacity. (Table) 

For 114 in. (by interpolation between 108 in. and 
120 in.) capacity per 1000 feet of line (2 conductors) 
= .001415 m.f. For 100 miles = 100X5.28 X. 001 115 
= .7471 m.f. 

b. Charging current. (Table) 

For 114 in. (by interpolation between 108 in. and 
120 in. we get .06165X10 - amp. per 1000 (Vet per 
1000 volts. 

Approximation of charging current per wire for 
the lino: 

.m;i5X10- 2 Xl!Mi < 5.28 X 100 -32.5 ai 

c. Self induction. (Tabic) 

I 1 4 in. (by interpolation between ion hi. and 
I2ii in.i we get .3847 milli-henries pel 
Self induction (single wire) for line — .3847X100 
103 I-' milli-fieni 

d. Inductive reactance (ohms). (Table) 
Values as given in til! \ 3 ■ i tance 

for a single wire. These values multiplied by the 
i per wire give 
tance for 1 14 in. I b 
108 in and 120 in.) we gel 2512 ohi feet. 



188 



GENERAL ELECTRIC REVIEW 



For total line (per phase) 
= 131.8 ohms. 
9. Natural period of line. 
7900 
\ LC 
L =203.12 milli-henries. 
C = .7471 microfarads. 
7900 



.2512X100X5.28 



P = 



= 454 



\ 203.12 X.7471X2 

From this we conclude that 00 cycles is a safe 
frequency. 

10. Voltage and current at generating end under 
full load conditions. 

Under this heading we shall make certain assump- 
tions which will greatly facilitate the calculations, 
and while they introduce approximations, still the 



Assume the following notation: 
E R = receiver voltage. 
£'= voltage across center of line. 
Eg = voltage at generating end. 

I R = current in receiving circuit. 

1 P — I R cos8 = power component of current, I R . 

Iir=Igsin8 = wattless component of current, 



Ic = charging current per wire for condenser 

at receiver end. 
I c " = charging current per wire for condenser 

at middle of line. 
Ic'" = charging current per wire for condenser 
at generator end. 






g_=J06ff£0__ 
Er=IOQOO0 







Fig. 16 



results attained are very close to the true state of 
affairs, and do not seriously affect the accuracy of 
the problem. 

Coiim ity of the line as concentrated 

shown in figure below. 
The gle-phase of the 

line as shown in Fig. 1 5. 

per phase (calculated 8d) £ = 131.8 
ohms. 

per phase = \ 3X22.86 = ^=39.55 
ohms. 






R 



= 19. 



Values of X and R just i ■ true 

values of reactance and resist e, but 

are thus designat tinual multiply- 

the fai tor \ '■'■■ ["hus I any phase 

taking thi multiplying 

bv the current per lej^. 

urrent along the line as separated 

:id wattless, and cal- 
culate the drop due to each. 



! wattless component current in section 1 

of line. 
/„." = wattless component current in section 2 

of line. 
/« = wattless component current in generator. 
I g = total generator curr 

The quantities together with their values for this 
particular problem are elearly shown in the vector 
diagram (Fig. 16). 
E R = 100,000 
I R = 128.2 

Ir <=I R cosO = 128.2 X.85 = 109 amps. 
I R sin8 = 128.2 X.527 =67.6 amps. 
cose 

rging current /,' for condenser at receiving 
end. 



z '-^ |(i«c £ *)«= 2 '/= 37 



KEY FOR THE COMPLETE CALCULATION OF A TRANSMISSION LINE 189 



C=' 



471 



hi" 



. ,_2X377X.7471X10 5 

c ~ 7^ — ~ = 5.4 amp;-. 

V3X6X10 6 

This is shown plotted in Fig. ](i 
/„,' =67.6-5.4 =62 2 a: 

Drop section 1 of line. 



\-~Ip = 19 

In phase C 7. 



'X109 



~,I'n = 65. 9X61'. 2 



ab 



In quadra- (f 7V=19 - 77X62 - 2 

ture 1 X , 

\t;Ip =65.9X109 



= 

= 4100 

= 6255 

= -1230 

= 718.3 
be = 5953 



Generator voltage full load I 1 1,3 10. 
Charging current I e '" for condenser at generating 
end ot line. 



1 3 I 6 J 

2 [ I X377X .7471X111.3401 

\ A Oxnr J =li -° 

amps. 
Current at generating i 

T L 

/„.« = 67.6 -34.5 = 33.1 

Ip= =109 

T i= I inn- - t :.:;.i- = U3.9 amps. 

K.v.a. at Generating End 

k.v.a. = \ 3E g Ig =1/3X111,340X113.9 = 

21.965 

Power factor generator end =~ — =.912. 




Fig. 17 



Add on the dr op in Fig. 16 as shown. 

E ' = ^Ob i +~bc~ i 

Ob = Oa +ab = 100,000 + 6255 = 106,255 
be = 5,953 

E ' = \ 106,255 s + .j, '.I.".:;- = 106,420 

Charging current for condensers at middle of line. 



Ic" = 



2 

2 
I 3 



4a>C£ 
6 



4 X377 X.7471 X 106,420 ] 

6X10 6 



= 23.1 



amps. 
I" =/V-/"« = 62.2-23.1=39.] amps. 



Drop^Section (2): 

I- 

In phase \ 7- 



'§//■ =19.77X109 



In quadra- 
ture 



= 65.9X39.1 



\'\l '„ =19.77X39.1 



65.9X109 



= 2155 

= 27.77 
ce= 1732 

= - 773 

= 
ef= 6410 



' I Ue 2 +ef 

Oe = Oc + ce = \ 06,420 +4,732 = .11,1 52 

e/= Mil. 

S*=l i ii.i:,2 i 6,410*- 1 1 1,340 



Full load conditions. 
Generating end. Receiving end. 
Load 20,000 kw. 18,87s lew. 

Voltage 111,340 100,000 

Power factor .91 .85 

K.v.a 21,965 22,209 

Loss on line 1122 kw. 
Per cent, total drop 11.1 per cent. 
11. Regulation of line (cos$ = 1.00). See par 
Vol. XIII No. 3 

Kilowatts generating end 20, 

Volt.!- receh ing end E R 100.000 

Resistance per wire, Ri 22.86 

From formula pagel41. Vol. XIII No. 3, we 

RiP .v, 

os*8 (1 - , 
In this case cos 6 = 1 

R,P 22.86X20,000X10* 



E^cos^B " in"' 



0457 



_ (2a+l)±] 4a 

2a 

t] lls - s ,,,,- 
ii:ni =•"' 

X, |)er cent. loss = 4.l."i per cent. 

0415 830 

Kw. delivered at receivin 

19,170 

/ \ i 19,170 

\mpercs at receiving end 

I 100,000 

= 1 11 



190 



GENERAL ELECTRIC REVIEW 



Charging current I c ' for condenser at receiving 
end =5.42 (calculated in 10) 
See Fig. 17 for graphic outline of problem. 

Drop Section (1). 



f X/a=19. 



•XI 10. 



^ XI c' =65.9X5.42 



-X/ r ' = 19.77X5.42 
r, XIk =65.9X110.7 



= 2189 

= 357 
a6=2546 

= 107 

= 7295 
be =7402 



Rise of Voltage at Xo Load. 
Consider the voltage at generating end as held 
constant between full load (cos = 1) and no load. 
At no load the voltage will rise in value from the 
receiving end of line toward the generating end. 
It will be sufficiently accurate to calculate the 
charging current using the value Eg (generator vol- 
tage) in each case since the variation in voltage 
alont; the line will not be so great as to seriously 
affect the results. 
See Fig. 1 8. 
E g = 107,110 

2T4X377X.7471 X107. 1 LI 



[' 



\ 3 
amp 

1 . 



6X10" 



Add the e drops in Fig. as shown. 
Voltage at middl e of Iine = £'. 

E '=\ Ob'+bc* 

Ob = Oa+ab = 100,000 +2,546 = 102,546 

be = = 7.4(12 

£' = ! l()2,.")4li- + 7 1nj =102.810 

1 C "=ZSZ 



ir^.s 



h' =tX23.2= 5. S amps. 
4 

Voltage Rise Section 2. 
f(l c "+7 c ') =1(23.2+5.8) 



19. 



2 Vc"+Ic) =65.9X29 

£' = \ 7J/T= -fbc* 
06 = 107,110 + 1911 

be = ">7:: 

£' = V 109. 021- +573* 



10 ] =23.2 



X29 = 
(6c) = 573 
= (06) = 1911 



= 109,(121 



= 109 022 



2r 4X377X.7471X102.810 ] 
c 1 :;L 6X10" J 

amps. 

Drop section (2). 

t^X/a =19.77X11(1.7 

^X(/c'+V)=65.9 • 



2 X(/ e '+7«") =19.77X27.72 
\ ■ I 65.9 ■ 110.7 



=22.3 



E 9 -/OZl/0 

Fig. 18 

Rise Section 1. 

I XV = 19.7 



*# 



7X5.8 



XI c =65.9X5.8 = 



= 115 
<:d=382 



E« = l Od^ + de- 
Od = 102,810+ 4,016 
de = 



= 


2189 


.72 


1S27 


cd = 


4016 


".72 


548 


= 


7295 


de = 


.SI 


UKi,826 
= 7. si:; 





2 X V I is negligible. 
.' ,£ f = 109 022 +382 = 1 09,40>' 
Regulation. 



109,400 

liMi.iKiii 

9, K") rise from full load to no load 



9400X100| 

100,0(1(1 



9.4 per cent. 



SUMMARY 



I inc. sly, • 7,843' = 107,110 volts. 

Charging Current Generator End / '" 

, „, 2T377 <.7471 X 107,1101 . „ 

Ic [ ( . X1(1 „ J =5.8 amps. 

1 11 1 ,1 I in : ,'u: =/ fi 





full 
ictor 


load 


Generating 
End 

40,000 kw. 
111,340 volts 
91 
13,930 


Receiving 
End 


1. Load 
Vl il 

Power f 
K.v.a. 


.'I7.7.">(> kw. 
100 000 volts 

85 
44,418 



Lo ■ on line 
Total drop full 
Regulation (cos = 1) 



2244 kw. 
1 1.1 per cent. 
9. 1 per 1 



I' = \ 1 10.7* +5.42» = 110.8 

'"=\ llo.s-'4-22.:!-=l 1:;. 

I 1 i ■ 1 13.1 amps, 



Pounds of conductor (cop: 2.115,000 

Total cost of conductor (both lines)*::i'>2.2.>o 
Annual interest on in SIS, 1 1 2. ."id 

Cost of lost power $22 140. 00 

(To be Conlinm 



191 



PRESENTATION OF EDISON MEDAL 

The Edison Medal was instituted by the American Institute of Electrical Engineers in commemoration 
of the twenty-fifth anniversary of the commercial introduction of the Edison incande i enl lamp, and for the 
first time was awarded to Prof. Elihu Thomson ''or meritorious achivement in electrical cieno . engineering, 
and the arts. The presentation was made at the annual dinner of tin- A.I.E.E., New York City, February 
24, 1910. In acceptance, Prof. Thomson spoke as follow 




Anything which I might say on this oc- 
casion could only express in small measure 
my appreciation of the honor done me in the 
award of the first Edison medal. To be 
selected by such a representative body of 
men, as distinguished in the electrical profes- 
sion as the Edison Medal 
Committee, is itself a 
sufficient recognition; 
one to be prized most 
highly. I most heartily 
thank the Committee. 

It is a source of great 
satisfaction that the 
award bears the name 
of the chief of pioneers 
in the field of large elec- 
trical application, the 
name of one to whose 
energy and courage, to 
whose ingenuity and 
resourcefulness the art 
owes so much. I know 
that all present will 
agree that the name of 
Edison is peculiarly 
fitting to characterize 
an award given for 
electrical achievement. 
While the period of in- 
vention and technical 
advancement through 
which we have been 
recently passing has 
affected all fields, with 
none has the influence 
upon our conditions of 
life been more profound 
than with the applica- 
itons of electricity. 

When we look back to the early beginning . 
we can realize the privilege of having lived 
at such a time so as to take sonic part in all 
that wonderful progress which has filled the 
succeeding years. 

Who can ''numerate the many conqm i 
of man ovei nature's forces; the unlocking 
of the treasure house of knowledge of the 
universe around us? Through i1 

acquires the ability to navigate the ail 
itself; an achievement which the most an 
quine of us could scarcely have the 




The- Edison Medal 

VU W K M INI riiC Tv. F_NTY-FlFTH ■ 
\NNIVE R\-«V i i' BFVI INTRO- 

DUCTION A\! i . 

< )i thi incandescent-lamp 

FRII r VTES \ND ADWIIU JVVOF 

Thomas • Alva ■ Edi son 
Fifty Slvlnth Birthday • 

EVENTH-NINETEfNHVNDREDANDFOVR 

■Mi-, \N ISSII l\TL Of F-irCTRK Al EN 

Meri HIEAtMLNT IN EXLCTWCJTY ' 

THU-CEKTIPI&S THAT TFE COLD-/ v *EOU- nv. &E£N AwAHntDTO 

Eli hv Thomson 

FOIC MErUTORIOVVACHILVf.Mf.NT- INE-LtCTRJCAL 

SCIENCF -ENGINEERING ANl-> ARIs As fAc.-'VUFIEDIN 

s I JUBVTIONS-TFtRE-TO-DVRINGTlt- PAST 50 YEARS 

AMERK \N INSTITVTE OF EULCTRIOM 






'***&£■ 



Certificate of Aw;«d 



would come so soon. Let us hope that all 
this is the beginning of an age of still greater 
advances, in which man will build more and 
more upon tin- foundations already laid. 

I have sometimes been asked whether I did 
not like to read what may be called scientific 
fiction; in which an 
author tried to picture 
future scientific pro- 
gress. I have usually 
answered "No," for 
"Truth is stranger than 
fiction." It is the unex- 
pected which happens. 
A speaking tube might 
suggest a telephone, but 
what writer of fiction 
was there to predict 
that such an inexpressi- 
bly simple arrangement 
of wire and iron could 
transmit speech before 
Bell did it. Who of 
them told us of the 
wireless telegraph, and 
that an ordinary simple 
induction coil could stir 
the ether and transmit 
signals over hundreds 
of miles? What fiction 
writer had imagination 
so penetrating as to tell 
us that we could >> 
day see our bones, and 
that surgery would be 

helped thereby? Who 

knew of the wonderful 
properties of radium, or 
everimagined them ■ 
sible? To come nearer 
home, who could picture as the man 
triumphs of electrical engineering- a dozen 
or more different kinds of electric lights: 
mission of thousands of horsepower "f 
over hundreds of miles; the el, 
railroad, and the oilier developments which 
in o hori a time have far outstripped our 
I ejetrava Lpectatioi 

A an instance of wha 
peopli at the early incepl ■ i i >ur art, I 

will read a little extract which I hap] 
to find in one of the issues of bight 



I HI' 



GENERAL ELECTRIC REVIEW 



Journal of 1878, when a discussion of the 
forthcoming Edison light, then the platinum 
wire lam]), was had. The following colloquy 
took plac< : 

Mr. D. — Tin- jj'i^ we arc now burning a 

from Birchington quarter 

miles. Would it In: possible fur me, if I wished to 

o si here ti > Bin hington 

e light there? 

Mr. ('.. It would nomi- 

Mr. D. Then how am I to light Birchington? 
Mr. G. — I should say. decidedly, t 

machines to Birchington. 

Mr. D. What am I to do for light along the 

road between here and Birchington? 

Mr. G. — Place mai h m i onvenienl Mi- 

es. 
Mr. I). In other words, several stations in 

such a short distani 

That was the view of a gas man and actually 
occurred at a meeting of gas engineers at the 
time reported, and will be found in the Gas 
Light Journal. 

I c< mid go on and multiply instances of that 
kind, but thai is merely a statement of con- 
ditions as they existed, and we have not time 
to go so far into ancient history. 

I have but little more to say in response. 
1 did not intend to make a speech of any 
length. 

I shall always value very highly the dis- 
tinction which has been accorded me. But 
however much one maybe rewarded for doing 
that which his tastes and inclinations have 
led him to do, there is. indeed, another and 
more immediate reward, the hope of attaining, 
which is after all the strongest stimulus; 
I have sometimes referred to it as the "jo] 
of accomplishment." It is the sen e ol 
satisfaction which accompanies the doing 
of a thin-, the surmounting of an obstacle, 
the attainment i oal. It is the pleasure 

of having tried, and in spite oi difficulties, 
eded. Those who have done this can 
understand what it meant. I confess that 
where a null is brought about by nun- 
pellinj i whole or part, the 

question of how muclicredi orded 



is not easy to determine. I am not arguing 
for the view of the ascetics that there belongs 
the greatest credit to those who make them- 
selves most miserable. 

It is sometimes the case that a difficult 
thing is a sort of challenge, appealing to the 
imagination. After all, to the artist, the 
inventor, the scientific investigator, the 
engineer and the broad man of business. 
imagination is often the chief mainspring of 
.action. It enables him mentally to picture 
a thing as done or accomplished before the 
doing, and so to seek out the plan to be fol- 
lowed or the measure to be taken. Imagina- 
tion furnishes the dreams that may come t rue : 
they are carried into practice, and if the 
things done are worth while, success and its 
accompanying "joy of accomplishment" 
follow. 

What matters it that there are many and 
unlooked for hardships, setbacks, and strug- 
gles, against adverse circumstances, if the 
end in view is at last attained? There will 
always be need of energy, self denial and per- 
sistence, if we would follow out our plans. 
Too often success is measured by financial 
outcome and this we must guard against. 
We need the broader view which causes us 
to sympathize with all progress and assist 
in it. 

I wish now to add that in honoring me you 
should not forget that there were' faithful 
co-workers — some of whom I see' now here — 
without whose help at times when it was most 
needed much less could have been a 
plished. I mean also to include in this 
those through whose wisdom and business 
, i city the means were provided for eloing 
such things as seemed needful at the time. 
To them a high tribute is due, for they con- 
tributed in large measure' to render possible 
that for which the Edison medal has been so 
gi i ton .].. accorded. 

Ladies and gentlemen, members of the 
Institute: I thank you till with the utmost 
sincerity for the honor you do me in being 
presenl on this occasion. 




VOL. XIII, NO. 5 



by General Electric < ompany 



MAY, l'HO 



CONTENTS 



Editorial 

The Single- Phase Induction Motor, Part I 

By Profs. J. II. Morecrofi vnd M. Akimm 

Commercial Electrical Testing, Part II 

By E. F. Collins 



L95 
L97 

L'lll 



A Motor-Operated Billet Mi 



By B. E. Semple 



I'll) 



The Elements of Transformer Construction, Part II 

By W. A. Hall 



LMi2 



Hyperbolic Functions and Their Application to Transmissiim Line Pn iblems, Part II 

By W. E. Miller 



220 



Underground Electrical Distribution 



By \V. E. Hazei i ink 



Motive Equipmenl for Electric Automobiles 

By II. S. Baldwin 



232 



Apparent Change of Ratio of Transfo ion in Three-Phase Transfoi 

By G. Faccioli 



235 



I- 



urnace tsci .m >mv 



23S 



P,\ P. W. C U.DWELL 



Book Reviews 
Obituary 



240 




REVIEW SUPPLEMENT AND TRANS- 
MISSION LINE CALCULATIONS 

The Review this month publishes a supple- 
ment in which the method of calculating 
transmission line problems by the use of 
hyperbolic functions is explained; two numer- 
ical examples being given to illustrate the 
method of working; i.e., a 300 mile line opera- 
ting at 60 cycles, using three No. 000 wires 
triangularly spaced 10 ft. apart ; and a line 
100 miles long operating at 2~> cycles, using 
three No. (I wires equally spaced in a plane 
with S ft. between centers. In the latter 
ease, approximate formula' are used which 
have been derived from the hyperbolic equa- 
tions. The formuke are given in the supple- 
ment with explanatory notes as to their use. 
The constants and hyperbolic functions neces- 
sary for the evaluation of numerical results 
are also tabulated. No references need there- 
fore be made to other publications or tables, 
and the supplement is complete and self- 
contained. 

As noted in the first part of Mr. W. 
E. Miller's article, the method followed is 
Kenncllv's, as given in McMahon's Hyper- 
bolic Functions. The work was undertaken 
in consequence of the discussion on Mr. 
Thomas's paper, at Frontenac, reported in 
the A. I.E. E. Proceedings for November, 1909, 
where more than one speaker referred to the 
hyperbolic method as that best adapted to 
transmission calculations, though there 
was considerable divergence of opinion on 
this question. Reference to 'lie upplemem 
oughl in remove any doubt as to the sim- 
plicity of the hyperbolic method, anil to 

■ m me. engineers of its ready application to 
tlr- solution of transmission problems when 
the constants and hyperbolic functions are 
properly tabulated. 

The second part of the ait i. le di )i U 

some length the physical aspe I of core 
viewed in accordance with one oi the modern 
theories of electricity the contrast between 



corona and capacity current being empha- 
sized. The law connecting the no load loss 
with the length of short transmission lines 
is also given. 

It must be understood that the formulae 
and constants given can be directly applied 
to transmission line problems only if the 
generator current and voltage follow a simple 
harmonic law; that is to say, only if harmonics 
of considerable magnitude are absent. The 
latter is generally the case, but occasionally 
the capacity or even the load current intro- 
duces harmonics into the generator waves. 
From oscillograph records these waves can 
be analyzed into their harmonies, and the 
formula' can then be applied to the funda- 
mental wave and each harmonic separately. 
Thi' constants, of course, apply only to the 
fundamental wave, and new constants must 
be calculated for each harmonic. 

In the present state of knowledge, it is 
impossible to include corona effed in the 
equations. Where the corona current is ecu 
siderable, the no load loss cannot be obtained 

front the equations, but they are sufficiently 

reliable in such eases for calculating the elec 
trical conditions along lines under load. 

The equations and discu isions refer to the 
electrical characteristics of transmission In 
after the normal state has been reached, and 
the transient phenomena which OCCUT when 

t he electrical condition • are suddenly changed 
are ignored. The method for calculating 
these is given in Steinmetz's "Transient 
Phenomena." Tliise phenomena are under 

certain circumstances extremelj important 
and it would be well worth while if numerical 
results were computed fo 

examples: i.e., a lone line on open circuil 
operal Lng a; 60 i cle i when erator is 

connected to the line at maximum volta 

and when it i ru volta 

The voli . and currenl ihould be plol ted for 
each ease tor different points along the line at 

the moment ritch and after 



L96 



GENERAL ELECTRIC REVIEW 



successive time intervals, until the normal 
state is reached. The advance of the voltage 
and current waves and their reflection when 
they reach the end of the line would then be 
graphically shown. 

If the calculations were made at many 
points along the line and al sufficiently clo 
intervals of time, and each curve were photo- 
graphed, the series ^o obtained could be run 
through a cinematograph machine and show 
a continuous record (if the phenomena by 
proi- en. This would he ex- 

tremely valuable from an educational point 
■ >f view, since such visual presentations help 
towards a physical understanding of the chief 
phenomena underlying tin- problem. Were 
mure uf the abstruse, and fur that matter 
the simpler, problems which enter into elec- 
trical engineering treated in this manner, 
much clearer ideas would be formed 
than can 1 ie obtained from discussions of 
or calculations from formula-. The labor 
and expense involved in the preparation uf 
I hese curves and their photographic reproduc- 
tion arc tar from prohibitive, so that there 
i nu reason why such methods should nut lie 
used occasionally as an auxiliary fur coll* 
training or lecture work. 

THE SINGLE PHASE INDUCTION MOTOR 

The R\ \n w is fortunate in being able to 
present with the present issue the first part 
uf an article on the single-phase motor, by 
Professors Morecroft and Arendt of Columbia 
University. This article, which the authors 
have kindly given us pi i print, 

was written to form part of a treatise on the 
sulijcct of il motors. The book, 

which will appear later, will include the 
art-' the synchronous a.c. motor and 

the d.c. scries motor that were published 
respectively in the May and June issues and 
the AugUSl and September issues of last 

year. 

Coming from this source, the editors have 
presumed to pass upon tin- accuracy 
the statements in the article, which, consider- 
ing the high authority of tin authors, has 
been left entirely with them. 

As with the arti ■ nchronous 

a.C. and the d.c. scries motor, our readers 
will find this discussion uf the single-phase 



motor of much interest and value. While the 
mathematics employed is not difficult, the 
authors have also presented their conclusions 
and much of the reasoning in simple non- 
mathematical language. 

The article begins with a description of the 
interaction between the impressed and in- 
duced magnetic fluxes, which is followed by a 
lucid explanation of how the revolving field 
is developed and the torque produced. 

The first part of the article closes with the 
torque equations and a clear statement of the 
conclusions to be deduced from their analysis. 

The second part, which will be published 
in the next issue, opens with the subject of 
the characteristic curves. A circle diagram 
for plotting the curves is described and the 
results in a specific case are tabulated and 
discussed. The various methods of starting 
are then taken up and concisely but amply 
treated. This second portion of the article is 
wholly free from mat hematics. 



UNDERGROUND ELECTRICAL SYSTEMS 

Under the title Underground Electrical 
Systems, Mr. W. E. Hazeltine has contribut- 
ed a remarkably succinct article covering the 
choice of conduits and cables for various 
classes of work; the subject Vicing treated in 
an entirely practical way, without theoretical 
discussion. 

The conditions to be met in underground 
systems are described; the material used for 
conduits arc then given, and the advantages 
and disadvantages briefly stated. 

The relative utility of single and double 
. of single and double manhole covers, 
the construction uf manholes and the methods 
of supporting the cables within them, are 
given briefly as are also the size of cables and 
the several kinds <<( insulation employed 
in different cases. The essentials to be 
lered in drawing in the cables and otln r- 
wise installing the systems are also treated. 

In short, the article forms a very complete 
and practical summary of the subject of 
underground electric systems. 



197 



THE SINGLE-PHASE INDUCTION MOTOR* 

P \KT I 

By Profs.'J. II. MoRECROFT and M. Arendt 
Columbia University 



In small single-phase alternating currenl 
plants, the constant speed motor thai i 
must extensively used i of the induction type. 
Structurally it is very similar to the correspond- 
ing polyphase machine ; f in fact any polyphase 
induction motor will operate as a single phase 
machine of somewhat smaller capacity and 
lower power factor, if it is at first caused to 
rotate at nearly synchronous speed by some 
starting arrangement. The necessity of 
providing some such auxiliary device ; 
from the fact that the single-phase motor, 
per se, has no starting torque. That such is 
the case may lie readily seen without the n 
introduction of mathematical proof. 



Absence of Starting Torque 

Consider a bi-polar sin e motor, 

provided with a squirrel-cage rotor. I : , 
distribution of current in the secondary 
at standstill is as indicated in Fig. 1. The 
current in bars <;<;' is zero, because these 
are equivalent to a closed loop the plane of 



The bar in. carrying currenl as indicated, 
will exert a torque upon the rotor, as shown 
by the arrow alongside it. However, owing 
to the symmetry of the secondary winding, 
for every liar m there is another m' having 
a current of equal amplitude bu1 ol 

C 





Fig. 1. 



Distribution of Current in Stationary Rotor 
of Single-Phase Induction Motor 



which i- located parallel to the flux. The 
maximum current i i I up in bars W. 

iv, i In equivalent loop, if it mo 1 
all, must move parallel to tl • n of the 

of force; hence H exerts no turning i i 

*Tm appear later as pai I of a 

tThc i C. B. L. 

Brown. See I. . V.. I. XXX. 



Short Circuited Coil Inclined to Axis 
of Oscillating Field 



sign. This latter liar being in a field of the 
same strength and direction as that in which 
m is located, will exert a torque equal to that 
ped by m. bu1 in the reverse direction, 
as indicated hy the- corresponding arrow. 
In the same way the efforl exerted due to the 
current in any liar of the winding will lie 
neutralized by thai of another bar symmetric- 
ally located with respect to the axis of the 

primary field; consequently at standstill no 
turning effort is developed and the motor 
fails to a© i 

The above fa< ma be proved as follows: 
A nine the rotor winding as composed of 
symmetrically placed short-circuited ■ 

and i on lider one having its plane at an\ 
.. to t he axis of the held \ \, a illustrated in 
Fig. 2. Further suppose the flux distribi 
to be i cosine function of a; this is approxi- 
mate^ i he ca c v, nil acl ual motoi proA ided 
with distributed stator windings: then let 
/; rep the maximum flux density at 

/{ i o.s pi is the in lux density at 

H COS pi t<" >r is I ■ lino. \ ah 

the in I elected, .and with .1 as thi 



198 



GEXERAL ELECTRIC REVIEW 



of the coil the flux passing through it becomes 

. 1 B COS pi COS alia = BA COS pi Sl')l a. 

(1) 

The e.m.f. induced in the selected coil is 

</'t> 
e= — — = BA p sin pi sin a. 




Fig. 3. Main and Quadrature Fields. Single-Phase 
Induction Motor 



The instantaneous value of the corresponding 
current is 

i = BA p sin(pt-e)siii a + Z'. 
Naturally in the case of a single coil this 
current will read upon the stator field and 
produce flux di tortion; bul as we arc going 

-I up the effects of all the rotor ceils the 
individual reactions balance and the field 
tion beo ible. I; is to be 

Doted thai the impedance of a coil will be 
modified by the action of the neighboring 
coils, consequently '/.' in equation Hi represents 
the effective impedance. The angle e = cos~ 1 
(r' -5- Z'), wherein r' is the effective resistance 
of the coil and /' the in:- as above 

defined. 

If there are n coils on the rotor equally 
1 from one another, the effort of the 
A'th coil will be 

/ =lB*Ap[sin(2 pt-e)+sin o]x 

sin — r-5-2 Z', I 

n 

wherein / is the length of one coil. 

The instantaneous torque exerted by the 
whole rotor is 



T = It = lB"-Ap{sin{2 pi-e) + sin e] x 

n 2 A" 

I. sin' -*+2 Z' = 0.* (5) 

u 

Development of Revolving Field 

We have just shown that when we have an 
oscillating magnetic field the rotor placed 
therein fails to exert any starting torque. 
Therefore, if a single-phase induction motor 
does develop a turning effort after it is caused 
to revolve, it must be because it has, by some 
reactions of the rotor currents upon the 
stator flux, provided for itself a rotating 
magnetic field. That such is the case may be 
shown non-mathematically. Assume a two- 
pole motor (Fig. 3) the stator winding of 
which is supplied with a single-phase alter- 
nating current, producing an oscillating field 
between the poles A A'. The rotor currents 
produce a field at right angles to the main 
field, and for convenience we will assume this 
to be represented by the poles BB'. In 
commercial machines no such empty pole 
spaces exist, as practically all of the stator is 
covered with coils. 

The inductors of the revolving rotor have 
c.m.f's., induced in them due to two actions; 
namely, by motion through the field and by 
'lie time rate of change of the flux threading 
the coils. The first we shall designate as a 
rotational e.m.f. and the second as a trans- 
former e.m.f. 

The inductors aa' will always have a 
rotational e.m.f. set up in them except when 
the stator tield passes through zero value. 
The amplitude of this e.m.f. for any given 
speed will he proportional to the instantaneous 
value of the stator flux. Conductors in;' may 
he considered equivalent to closed coils, and 
the current flowing in them will produce a 
field in direction BB'. Neglecting tempor- 
arily the IR drop in the rotor, the e.m.f. 

induced in aa' may be placed equal to , 

at 

where <K denotes the cross field developed by 
the currents due to the motion of the rotor 
in the main field. The rotational e.m.f. is in 
time phase with the main field, hence Un- 
cross held *, will tic in time quadrature with 
it. The direction of the main field and the 
motion of the rotor inductors are such that 
the e.m.f. generated in mi' is positive. t The 
rotor currents arc in such direction that when 
pole A is of north polarity- and decreasing, 
pole B will he of like sign but increasing, 

•This same result is obtained from analysis of equa. 16. 
tCurrents flowing away from tin- reader into the plain 
paper are called positive 



SINGLE-PHASE INDUCTION MOTOR 



l-.i'.i 



reaching its maximum strength one quarter of 
a period later. The strength of pule B 
decreases after a similar lapse of time, the 
main field reverses and a north pole begins to 
build up at A'. Thai is, the main field and 
quadrature field so combine thai a north pole 
travels around the stator in the direi lion .1 A'.i '/->" 
at synchronous speed. Hence, there exists a 
rotating field produced by the combined 
action of stator and rotor currents. This 
simple explanation gives an idea of the 
production of the rotating field in the single- 
phase induction motor, bu1 it doe ao1 
consider all the reactions which occur. 

The inductors hb' moving in the quadrature 
field have a rotational e.m.f. induced in them. 
in the same manner as those passing through 
the main field, and this is of maximum po 
value when the north pole at B attains its 
highest value. In addition to these two 
rotational e.m.t's.. the varying fields AA' and 
BB' set up transformer e.m.fs., in coil groups 
bb' and aa' respectively. Consequently, 
there are four e.m.fs., to be con idi re I I 
the actual rotor currents which produce the 
quadrature field can be determined. 

The rotational e.m.f. induced in inductors 
aa' is of maximum positive value when the 
pole A is at its greatest north polarity, but 
the transformer e.m.f. set up in these bars 
by the quadrature field is at the same momenl 
of maximum negative value. Hence the 
actual e.m.f. (£<;) existing in AA' is the 
algebraic sum of these two voltages. The 
rotational e.m.f. due to the main field must 
be greater than the transformer e.m.f. of 
the quadrature field; in fact the latter is of 
such strength that the actual e.m.f., Ea, will 
be just enough to establish the current which 
produces the field BB' . Since this quadrature 
field is at right angles to the main held, its 
m.m.f. cannot be furnished directly by the 
Stator magnetizing current, so we must 
investigate further to ■ il is taken, as 

it must be, from the line. It must bi n 
membered that the impedance of the 
coils is here assume 1 to bi uch tha the TZ 
drop is negligible; if this is not the case, the 
rotational and transformer e.m.fs. will not 
be in time oppo ! and their vector sum 

id of algebraic sum, must be con idered. 

The main field, by trai 
induces an e.m.f. in bars bb', and this is 
opposed to the e.m.f. developed in the 
inductors by their motion tl rough the 
quadrature field. The resuliani e.m.f. Eb 
in these conductors sets up a current affecting 



the main fieldand, consequently, the current 
drawn from the line. The current flowing 
in inductors bb' due to Eb is equal to 
that existing in bars aa', which is that 
producing the cross m.m.f. Moreover, the 




Fig. 4. 



Forms of Rotating Field at Various 
Rotor Speeds 



tit bb' is in such direction that it in- 
creases the magnetizing current taken from 
the line, the increment being thai which 
would be necessary to direciK magnetize the 
quadrature field. The reluctance of the cross 
field's magnetic circuit is substantially the 
same as that of the main field isequently 
the m.m.f. required for both will be the same, 
and obviously, therefore, a two-phase motor 
run on one phase will draw twice its normal 
current. This conclusion is 
out by actual practice, tests showing 
thai the magnetizing current of a single-phase 
motor is double that taken per phase by a 
two-phase and threelimes that required by a three- 
phase machine, the potential dijfereni e, frequt >:• y 
and turns per phase winding being the same. 

At synchronous pee. Is the two component 
fields are of equal strength; accordinglj they 
combine to give a circularly rotating 
Below synchronous speed the i e.m.f. 

in the bat in in\ erse propor- 

tion to the slip, and I tru I he quadr. 
field diminishes, while the main field remains 



•21 ii I 



CEXERAL ELECTRIC REVIEW 



constant. Consequently the rotating field 
developed below synchronous speed is of an 
elliptical form, the shorter axis being in the 
direction of the quadrature field BB'. When 
driven above synchronous speed the field is 
also of elliptical form, the major axis, however. 
being in the direction of the cross field. The 
field forms for different speeds are as illus- 
trated in Fig. \. a. b, c, respectively, corres- 
ponding to synchronous, sub-synchronous and 
suj ler-synchronous S] leeds. 

The maximum torque which a motor is 
capable of exerting, other things being equal, 
depends upon the average value of the 
magnetic field in which the rotor move-. 
This mean value, neglecting IR drop and 
leakage, is in the polyphase induction motor 
independent of the slip, while for the corres- 
ponding single-phase machine the average 
value of i he field decreases as the slip in- 
creases; thus the pull-out torque of a poly- 
phase machine connected single-phase will be 
less than when normally operated. 

Main- interesting facts concerning the 
rotor currents as well as the development of 
the rotating field may be derived through a 
simple mathematical analysis. Let us con- 
sider the elementary bipolar singli 
induction motor repn in Fig. 5 with a 

coil at an angle a to the main polar axis. 
Assume as before that the flux distribution 
is a cosine function of time, and adopt the 
following notation: 

A =area of coil. 

w = angular velocity of the coil, or«= «/. 
I sin a = sin u-z = projected area of coil 
on plane ( (" perpendicular to the flux NS. 

B = maximum flux density, its instan- 
-. alue 1 ieing /•' i os pi. 
Instantaneous flux interlinking coil a is 

* = j45 cos pi sin uil 

= h . I Bysin {p+w)t—sin(p- «) A 

the e.m.f. induced in coil a is 

e=--~ = ^AB ((p-o,)cos(p- u )t- 

(p+o,)cos(p+o,)t) 

Let r, and A, represent respectively the 

ctive resistance and inductance of the 

coils; the values of these constants being based 

not only upon the character of an individual 

coil but also to -nine extent upon the action 
of neighboj oils. With this notation the 

current in any secondary coil can be considered 
as resulting from the e.m.f . of equation 57, or 



7 = 0.5 AB 



( 



p— 0) 



(n , +(#--) , £i f )*' 



cos[(p+o,)t-e.J{\. 



wherein 



and 



9l - CM ~ 1 (n a +(/>-<W)' 



(riH-(#+-)«£i*)*- 

The flux produced by one rotor coil and the 
main field will so react upon each other that 
the value of the secondary current, if but a 
single coil be considered, can only be ex- 
pressed by an infinite series. It has been 
experimentally shown, however, that the 
flux-distorting reactions between primary and 
secondary do not exist with a rotor winding 
composed of a number of coils which 
divisible into pairs, the members of which are 
placed at '.hi degrees (electrical) to each other. 
The rotor winding of a commercial machine 
substantially satisfies this condition; con- 
sequently the higher harmonics of the rotor 
current disappear and the current is correctly 
represented by equa. given above. This 
equation indicates that the rotor current 
consists of two parts having different fre- 
quencies and amplitudes. 

At standstill, any coil spaced an an, 
from the axis of the magnetic field will have 
a current of the following form: 

which shows that the secondary current at 
standstill is of line frequency, ''"he current 
component with frequency ( p — , ases 

in value as th( speed rises toward 

synchronism, being zero at that limit, and 
the secondary current then becomes 
.1 /•>'/> i ev'2 pi ■ y H syn) 
(r*+2pl 
which is of double-line frequency. 

These variations of rotor current frequen- 
cies as well as the presence of the differential 
(p— «> and additive (/>+«) components may 
be conveniently observed by the application 
of a reed frequency meter. Connect such an 
instrument across the slip rings of the wound 
rotor of a polyphase motor, excite the stator 
with single-phase current and then 
the machine. As the speed of the rotor 
increases the frequency meter will indicate 



/ (syn) 



(10) 



SINGLE-PHASE INDUCTION MOTOR 



201 



the presence of two currents, one increasing 
and the other diminishing from the line 
frequency. 

Let us now select a coil on the rotor dis- 
placed any angle p from the loop a we have 
just considered. Fig. 5. The flux through 
this new coil at synchronous s peril («= ut = pt) 



indicates thai the pole rotates hark wards on 
the rotor. The latter, however, is turning 
forward at a rate pt, consequentlj the rotor 
poles revolve backward in ipace a1 a rate pt, 
and the equation of I his pole in spaci - 



HH- 



pt. 




Fig. 5 

will be, from equa. (i, 

*= AB cos pt sin (pt+p), 

= —-\sin(2 pt+p)+sin fi\, (1 



Coils Inclined to Axis of Oscillating Field 

If the equation for the current in the general 
coil is referred to the magnetic axis instead of 
to 1 he reference coil, we have 



It 



c.m.f. coil p = e = - -jj = -Allp(cos 

2 pt+p) 
current coil p = 



Kicos\(2 pt + p-e) + 



ABp 



(12) 



= A" cos 



H) 



(:+«--/") 



cos(2 pt+p-e), i 13) 

= K lC os{2 pt+p-e). (14) 

The total magneto-motive force of all the 
coils on tin-' rotor may be expressed as KiSi. 
The maximum m.m.f. exists in the plane of 
,ii i oil in which the current is equal to zero, 
and hence the poles of the rotor will be in the 
same plane. Le1 d' be the angle of that 
particular coil ; then 

i= K\cos{2 pt + p' ' — e). 
But since i is equal to zero, 
K t cos(2 pt + p'-e)=". 
whence 



and 



2 pt + p'-e = { 



*'=(| + «)-2 



'I" ,ii , . referred to the magnetic axis of the 
rotor the currenl distribution is constant; 
hence the m.m.f. of these currents i constant 
and rotates backward at synchronou peed, 
as above proved. 

The relative value of th< stator and 
rotor m.m.l's. may be derived as follows: 
Assume the rotor stationary; this corresponds 
to considering it as the short-circuited 
ei i Hidai'v of a transformer. Thus I he 
relations existing between primary and ei 
ondary m.m.f's. of a transformer apply or, 
n, gled ing resi itance and leal ag( , the econd 
ary m.m.f. is equal and opposite to thai ol 
the primarj . The currenl distribution in the 
otor on the basis of the above 
assumpl ion is expi i qual ii 

AHp 



',,= 



pt. 



\ r 






PL 



si lit pt - $)sin ,i. 



which upon neglecting r makes j = 



This means that the angle between the 
reference coil and the magnetic pole of the 
rotor changes at the rate of —2 />/. It also 



es to 



[Bp 

pt sin ti\ 
pL 



202 



GENERAL ELECTRIC REVIEW 



This, if / = 0, becomes 

AB . 
r = sin p. 



(15) 



It is to be noticed that when / = 0, the equa- 
tion of the rotor currents at synchronous 
spied equation (13) reduces to 

lr = 7= COS (fi-8) 

V r '+(2pL) 

which can be still further simplified, if r is 
negligibly small with respeel to pL, to the 
following form 



AH . J 
h= — ,, stn p. 



(16) 



Comparing these values of /„ and i, we see 
that these currents have the same distribution 
in the rotor, bu1 thai amplitude of the latter is 
only one half that of the former. Consequent- 
ly, since the m.m.f's. of the stationary rotor 
and of the stator are equal, the m.m.f. of the 
synchronously revolving rotor is one-half 
thai of the stator winding. 

The magneto-motive force effective in 
developing the flux B cos pt. when the two fields 
coincide, may be expressed as Y—X, wherein 
Y represents the maximum m.m.f. developed 
by the stator and A that due to the rotor. 
But, as above shown, X=Y-i-2, hence the 
excitation necessary to produce the flux 
B cos pt throughout the magnel ic circuit of the 

machine is , . or X. 

The two magneto-motive forces acting at 
any instant in this type of machine are: 
Y cos pt. stationary in spai e, 
X, constant in value, but rotating b; 
ward a1 synchronous speed. Since .V rotates 
backwards it may be written A' = .V cc. pt 
— X sin pt. and consequently Y—X, the total 
magneto-motive force acting at any instant, 
becomes 

1' COS pt - X COS pt \ X sill pt= X COS pt + 
X sin pt. 
This means that the total m.m.f. acting at any 
instant is oj constant value and rotates forward 

iu hronous speed. 
The magnetic reluctance of commercial 
motors, due to the use of uni- 
formly distributed windings, is practically the 
same, whatever the axis of the field; con- 
sequent!) the read ions existing between 
stator and rotor currents produce at or near 
synchronous speed a circular i field, 

and the formula' which applj to polyphase 
motors maj lie utilized. Theeffect of leakage 
and rotor resistance will modify this rotating 



field somewhat, changing it from circular to 
elliptical form. 

Torque Equations 

It has been shown in the derivation of 
equa. 8 that, when the secondary of a single- 
phase induction motor is caused to rotate at 
any rate u, its current may be expressed as 

U.I-X,-' 

,1- <*±4 X 



_AB/ (p- 
2 V\ 'i*+« 



C0S[{ p— u)t— I 

cos[(p+ u)t- e 2 ]\ 

Inspection of this equation shows that the 
rotor current is composed of two parts, one 
of a lower and the other of a higher frequency 
than the rotating field. We may consequently 
consider that this current is set up through 
the action of two synchronously rotating 
fields, one revolving in the same direction as 
the rotor and the other oppositely.* The 
frequency of the rotor current component, 
due to the suppositional field revolving in the 
same direction as the rotor, is naturally less 
(by the velocity of the rotor) than synchronous 
value or it is (p—a). The component due to 
the oppositely rotating field has a frequency 
higher than that of the line, its value being 

The per cent, slip of the rotor with respect 



to the field first is 



to the seci tnd field it 



(V) 



Kin, and referred 



Kill. 



The effective turning effort of the motor is 
the resultant of the interaction between the 
rotor current and two oppositely rotating 
fields. But, since the rotor and on< field turn 
in the same direction, the torque due to this 
latter field must be greater than that set up 
by the other. The torque developed by a 
polyphase induction motor may be expressed 
by the following equation: 

T - ^ " ' '' ' 

%i(r 2 H-5 ! * a ' 

wherein s is the per cent, slip between rotating 

field and rotor ci ire; A . inductors in series per 

oi the rotor: c. volts per turn; rj,resist- 

reactance at standstill per motor 

phase, and ua = p. the angular velocity of 

the revolving field. We may accordingly. 

Torino, Series II. 
Vol. XLIV. December, 1893. igea Hi). 

L29, 152, 1st I ond in 1894 



SINGLE-PHASE INDUCTION MOTOR 



203 



write the two component torques existing in 
the single-phase motor as 

wi(/ 2 - + ir .v..-) 
/»=— ; — — — ;; — — . wherein 



Sl = 



Sn = 



p — ol oi\ — CJ 



and 



/>+< 






The total effective torque is 



T=Ti+T 2 



.V -j -V-r 2 ( a- — j] i ( .v,.v.j .v-j- — r 2 ") 



(17. 
wherein s 2 — sj is positive for speeds below 
synchronism, while sis? is variable but never 
greater than unity. 

Analysis of this equation brings out the 
following facts: 



than its resistance. Unless such is the case 
,vi.v.j .v./ J — /•./-' will have a negative value, which 
means that the machine would tend to 
develop a negative torque or ad as a gener- 
ator. Fig. ii indicates how the speed-torque 
curves of a single-phase induction motor are 
affected by change in the value of rotor 
resistances. Curves .1 and B may be con- 
sidered as representative of standard ma- 
chines. Curves C and D indicate the effects 
produced by inserting relatively large resist- 
ances into the rotor winding. It is apparent 
from these curves that the introduction of 
resistance into the rotor circuit for pui | 
Of speed regulation is attended by a marked 
reduction of the overload capacity of the 
motor, and cannot be used as conveniently 
or advantageously as with polyphase motors. 
It is, however, employed to limit the starting 
current . 




0+25 50 75 100 125 150 

Percent Rated Torque 
Fig. 6. Speed-Torque Curves of Single-Phase Induction Motor, with Different Values of Rotor Resistance 

1. That the torque of the single-phase 



machine varies as the square of the impri i I 
voltage, this Vicing the same relation as 
obtains in polyphase induction motors. 

2. That the motor exerts no torque at 
standstill because st—st then equals zero, which 
fact makes the numerator of the same value." 

■'!. The motor cannot operate at synchro- 
nous speed, because this makes Si zero, in 
which case the torque developed is of negative 
value (si$2 X2 2 —p2* reducing to — r^ 2 ), and the 
machine tends to ad a a generator. Con 
equently the single-phase induction i 
must rotate at less than synchronous 

1. The fact that the maximum value ol 
unity indicates thai the ingle phase induction 
motor cannot operate unless the reactanci 
of its rotor winding at standstill is gri i 

i ■ >) 1(8 



."). The torque developed by a polyphase 
motor operated as a single-phase machine is 
less than that produced when normally 
connected, because of the presence of the 
counter torque / '■■. 

6. [f we take the first differential coeffi- 
cient of equation (17) with respeel to r 8 and 
u equal to zero, we find thai the maxi- 
mum torque developed Eoi any rotor 
u exists when 

r, = ( .»-,.*,.?., 1 3 -M 
and that the maximum torque 

/ \ - _ Jl })^.„, r8 . 

This equal ion show 
elected ipeed is greater I he le i the value of r». 

ontinutd. ' 



204 



OK XERAL ELECTRIC REVIEW 



COMMERCIAL ELECTRICAL TESTING 

Part VII 
By E. F. Collins 

ROTARY CONVERTER- Cont'd I 



D.C. Circulating Current 

Fig. 32 shows the connections for two 
three-phase converters wired for a pump back 







008000000fltP 

dlwnt Titid 



K 



T_? 






ireoooooo 
Serif jF/i?/d 

— TTffWooooooo^n 

S/wntfir/j 



# 



-<K'- 



<K'- 



foojtsrtaSt/ p/t/y tfLejjfS 



Fig. 32. 



Connections for Pumping Back Rotary Converters 
Without the Use of a Regulator 



run without a potent ial regulator to 

control the load. The core losses and (''A' 

supplied from the direct current 

end. The diagram shows, also, the standard 

starting panel, which should always be used 

when I wo o >m erti r i are tested t< gether. 

To start the rotaries, for instance No. 1. 

lie shunt field switch and the switch A". 

the latter short circuiting the armature of the 

upply. Note that the shunt fields are 

wired across the core loss supply, which in 

turn is wired to buses B and C of the starting 

panel, and that the series fields are left open. 

Throw switch A to the left and slowly reduce 

the resistance of the water until it is 

practical! ircuited. when tile switch 

5 may be closed. The blade of the water 

rheostat is now drawn out of the water and 

the switch I thrown to the right. .Machine 

No. 'J is then started in a similar manner. 



The field strength of each machine is then 
reduced until both machines run at normal 
speed. Next connect a number of incandes- 
cent lamps in series, the rated voltage 
of which is equal to the sum of the 
machine voltages across rings .1.1: i.e., 
across switches located on the dyna- 
mometer board. Two sets of lamps 
should be provided, one being con- 
nected across one of the switches while 
the other is stepped across each of the 
other switches in turn. Should one 
set show a rise and fall in voltage 
displaced in time with relation to that 
of the other, the two phases are re- 
versed and must be corrected. When 
all phases show a simultaneous rise 
and fall, the machines may be phased 
together and their speeds brought to 
the same value by changing the field 
on one of them. When the time be- 
tween rise and fall I >f v< iltagc. as sh( >wn 
by the lamps, decreases to a period of 
five seconds or longer, all switches arc 
closed simultaneously and the lamps 
become dark. 

During the period of starting and 
phasing the machines together, the 

fields of the booster should be opened 

and the armature short circuited. 
When the rotaries arc synchronized, 

the switches across the armatures of the 
boosters are opened and a weak field applied. 
the line meter on machine No. 1 being 
watched. The reading of this meter should 
reverse from that given on motor load, if 
machine No. 1 is taking load as a rotary. By 
reversing the booster field either machine 
can be made to run as a rotary. 

After balancing the current in each phase, 
full load phase characteristics may be taken l.\ 
holding the speed constant by means of the 
field of the inverted machine, and the load 
constant by means of the booster, the shunt 
field of the rotary being varied throughout 
Mgc and the current input nail. Fuil 
load voltage ratio should next be taken, 
after which the heat runs may be made. 

A line shunt must be used in each side of 
tlic direct current circuit, otherwise one line 
will have more resistance than the other and 



commercial lllctrical testing 



205 



the currents flowing through them will have 
unequal values, the unbalanced current 
returning through the alternating current 
mils of the machines. The currents in these 
lines can be balanced by decreasing the 
resistance in the low reading line. 
The direct currents should be bal- 
anced before attempting to balance 
the alternating current . 

In running a pump back test there 
will be a slight difference in the direct 
current voltages of the two machines, 
equal to the CR drop of the set. The 
held of the inverted machine will be 
less than that required for minimum 
input and will carry the additional 
current necessary for supplying the 
core losses. 

This method of supplying the ("-'A' 
losses from a booster requires such a 
large low voltage booster that it is not 
often used, except for small rotaries. 

With a Booster in the A.C. Side 

A second method of pumping back 
ries on full load heat runs is to 
use an induction voltage regulator in 
the alternating current side of the 
machines, as shown in Pigs. •'!•'! ami 34. The 
regulator is connected with its secondaries in 
series with the alternating current line and 
its primaries across the alternating current 
terminals of the inverted machine. It is 
always preferable to connect the regulator 
between the inverted rotary and the dyna- 
mometer board. The regulator takes the 
place of the booster used in the previous 
method, and is very satisfactory for supplying 
the ("-'A' losses. 

Starting the machines, cheeking the phase 
rotation, phasing in, and other operations 
already described, are repeated with this 
method. Always see that the regulator is 
Se1 al the no boost point before phasing in. 
otherwise load will lie thrown on when the 
switches arc closed. 

Load is increased by turning the core of the 
regulator in the direction of boost, the 

tenmeter of machine No. I being watched at 
the same time. If the reading reverses from 

■ r load, then No. I is running as a rotary; 

if, however, No. I does nol reverse, the 
regulator should be turned in the opposite 
direction. This shows that the regulator 
is wrongly connected in reference to hs 
markings; there is no necessity, however, to 
change connections. 



Using A.C. Loss Suppy 

If, instead of supplying the losses from a 
direct current source of power, an alternator 
is connected across the alternating current 
lines, between the inverted rotary and the 




Lessdufp/y 



To Tap/ s . 
ffldffoxes 



Fig. 33. 



Connections for Pumping Back Rotary Converters 
with Regulator 



regulator as in the preceding method, the 
losses can lie supplied at the alternating 
current end. When the alternator is large 
enough to start the rotaries, the wiring on 
tin' direel current end is greatly simplified. 
Tlic starting panel is omitted and the shunt 
fields are connected according to the print of 
connections for the machine. Load is ob- 
tained by means of the regulator as 1 i 

and the lest carried out as already de- 
scribed. 

If the alternator is too small to start the 
machines, the latter may be started singl] 
from the direci current side as before, and 
the two phased together. The alternator is 
then synchronized with the pair. If onlj one 
machine can be started by the alternator, 
bring it up to speed, open all its circuits, and 
lit it run by its own momentum whili the 
econd machine is quickly started. The 

ition is then remi ived from t he altei i 
field and t he .witches on the first niacin i 
closed. Excite the alternator field and bring 
Lot h machines up o er. After 

the ni.H hine are onci tarted, I he, can be 

broughl up to speed without an excessive 
current from the alternator. 



206 



GENERAL ELECTRIC REVIEW 



Alternating Current Generators 

Compleu Tests consisting of special tests 
and temperature I 

Special tests include saturation and syn- 
chronous impedance, and from these the 
regulation of the machine is calculated as 
ws: 

Let I' = normal voltage line, C = amperes 
line, R = hot resistance between lines. 

Kw. 
For three-phase machines C = ... 

\ oltagc \ 3 



For two-phase machines C= , ,. 

2 \ ( 



Kw. 



fte/J.. 




Shop 
5/>op Sw/tc/i 

Sw/tc/) 
7^ 







Fig. 34. Tabic Connections for Rotary Converter Pump Back 

For three-phase machines, voltage drop in 



armature, L\R\ = 



N I R 



For two-phase machines C\R,=CR. 

Let ai = amperes field on saturation curve 
corresponding to V~\rC\Ri and <Z2 = am] 
field "ii the synchronous imped o curve 
correspi mding to ( '. 

The amperes field required to produce 
il rated voltage with full load on the 

I em rator will be o 3 = \ a , 

Let the voltage on the saturation curve 
esponding to ,/., = \\. 

V\— I" 

Then the per cent, regulation = 

If it is desired to calculate the regulation 
of the machine at any power factor, then (' 

( 

,, ,. and Oj= n „■ . ■ a . ■;■'■ sin (I 
i 1 . /• . 

when e is the angle of which the per cent. 
power factor is th< 



Input-output efficiency test is made by the 
input-output method. 

Standard efficiency test is made by the 
method of losses. 

The calculation of a standard efficiency 
test is made as follows: 

Let Vi = volts line 

II' ■■= output = \:i\'i_ (.'/. for three- 
phase and 2 Vl C. for two-phase 

Cl = amperes line Ri = hot res. of 
armature between lines 

t'i = amperes field 

#2 = hot res. of field 

II, = open circuit core loss corres- 
ponding to V i, + CR on the core 
loss curve 

II'; = short circuit core loss corres- 
ponding to Cl on the short 
circuit loss curve 

II, = friction and windage obtained 
from core loss tesl 

C'i is calculated for each load, as in th< 
for regulation. 

CR = the drop in the armature = >'j C L R\ 
for three-phase machines and C'/. Ri for two- 
phase. 

IW=W& \ ir, + H' : ,-K C L Ri+C R, 
for three-phase machines 

= II', + :' i ir-:+H', + 2 CY-fl.-H a 
for two-phase machines 

Watts input = W a = W b +1 W 

W_ b 

W a 

II". need not be considered if the machine is 
furnished without base, shaft or bearings. 

The above method of calculation is used 
when the machine is to operate at unity 
power factor. 

If it is desired to calculate the efficiency at 
any power factor, the following calculations 
must be made. 

c,= r,x ^x\ i'F. ;,ml 

II' . = s.-iXl'tXCLX'; P.P. for three- 
phase machines. 

Kw. , 

c,= r,x2x\ r.F. and 

II' = 2V L XC L X' , P.F. for two-phase 
ines. 

C] should be calculated for various power 
irs as given under regulation. 

The change in the line current will affect 
(',. II',. II'-j. and the ("-'A' of the armature. 
See Fig. 35 and Table XIII. 



Efficiencv : 






COMMERCIAL ELECTRICAL TESTING 



207 



Non-i»ductive normal load heat runs con- 
sist in running the machine under normal 
load at unity power factor until constant 
tempera Hires are reached. These final tem- 
peratures are then recorded and readings 
taken of regulation with unity power factor. 

Non-inductive overload heat runs consist 
in bringing the machine to normal load 
temperatures, applying the overload at unity 
power factor for the specified time, and 
recording the overload temperatures. Read- 
ings for regulation at unity power factor 
should be taken. 

Normal load and overload power factor 
heat runs arc made in the same way as n< irmal 
and overload non-inductive runs, excepl 
that the machine is operated at a specified 
power factor. Wattmeters should be used 
with the voltmeter and ammeters to deter- 
mine the power factor. 

SYNCHRONOUS MOTORS 

The preliminary tests taken on synchronous 
motors consist of drop on spools, air gap, 
resistance measurement, balancing of phase 
voltages, phase rotation and running free 
minimum output. 

Complete tests consist of special tests and 
normal and overload heat runs. 

Special tests consist of starting tests, open 
and short circuited core loss, saturation, 
synchronous impedance, no load and full load 
phase characteristics, and wave form. The 
method of taking phase characteristics has 
previously been described. 

Starting tests should be made both with 
and without a compensator, if the motor is of 
a new type and rating and is to he started 
with a compensator when installed. If the 



motor does not form part of a motor-gener- 
ator set, it should l>e belted to a generator 
so that it will have some load at starling. 



90 
BO 
70 

\*0 

% 
^30 

\<o 

**> 

20 
10 




T-V<-----)f- :z T- =: ^ :: ~^ T 


/ M l 


4 __» 


-. 


]::::::::::::::::::::::::::: 


::::::::::::::::::::::::::: 


E::::::::::::::::::::::::::: 







220 ■ 
2O0 

I80 

/to ■ 
i*0 ■ 

%/20 - 

N 

£ ZOO ■ 



eo sc 
%£.oact 







































ii. 










































F 


__ 


































J L- 


— - 






























Ji 


it 








--- 






















-- 










1c 


•f 


' 








1 








\»- 






















T 








-< 
\ 


i 








r 






































* 






























■^v 








" 


M 
1 


ir 


elo 


Mi 


















































-i 


C— 






L - 




































































































































































































































































































































































































































































































fr/ct'Oi 


Z2. 


£f 


pffa 


fog 












== 










-tVks^ 


— 


- 


k 


== 




^Lo.otfl 


— _-— 









60 30 



Fig. 35. Efficiency and Losses on a 5000 Kw., 
11000 Volt, 3 Phase AC. Generator 



TABLE XIII Eff. and Losses of a 5000 Kw., 11000 V., 28 Pole, 60-Cycle, 3-Phase Generator 



' , Li I 111 

V.. Its Line 
Amps. Line 
Amps. Flil. 
CR 

V+CR 
' Loss 

'. Short Cir 
C*R Arm. 
C'R Flil. 
Friction 
Total Losses 
Kw. Output 

I Input 

', Efficiency 



1 




14500 

25000 

182500 

ii 

182.J 





ucoo 

224 

12 

I L012 

1 13000 

L330 

1 :,( ii ii i 

25000 

184330 

1250 

1434 

87.3 



.',ii 

1 1IKI0 

l.il 

228 

24 

I MIL' I 

I 13100 

21 ii i 

5320 

15600 

25000 

189220 

1500 

2689 

93.0 



7."> 


Hill 


1 25 


1 lillill 


11000 


11 


196.5 


262 


317 


235 


245 


257 


36 


IS 


;,n 


1 1036 


i mis 


1 1060 


1 13600 


144100 


1 17 ) 


581 1 


1300 




12000 


21300 


31 100 


[6600 


1 SI 11 III 


P. LSI III 


25000 


2 jinn 


25000 


197700 


I'll! 170(1 


225400 


3750 





6250 


39 is 














Res. Arm. (Line) .1927 Ohm 25 C 207 Ohms Hot. 
Res. Fid. .2795 Ohm 25" C. .3005 Ohms Hot. 



208 



GENERAL ELECTRIC REVIEW 



The motor should first be tested for starting 
without the compensator. The center line of 
one pole is placed in line with the center line 
of the frame and ISO* electrical degrees 




Fig. 36 

marked off in a clockwise direction from this 
line on the head end of the motor. The 
total length of this scale should be two-thirds 
of the distance between the center lines of 
adjacenl poles for three-phase machines, 
one-half for two-phase machines, and one- 
third for six-phase machines. The scale 
should be divided into four equal parts, each 
division line being numbered. On each one of 
these scale divisions, the center line of the 
marked pole should he placed and the motor 
started. Thus five tests are made to insure 
that the motor will not stick in any position. 
See Pig. :i(i. 

With the pole A moved to position No. 1 
and the machine at rest, sufficient current 
hould be sent through the armature to give a 
reasonable reading of amperes ami volts on the 
various phases, and induced volts on the 
field. The induced volts field should lie read 
by a potential transformer and alternating 
current voltmeter. These readings are taken 
to determine which phase gives maximum 
readings of currenl and voltage. 



The voltmeter and ammeter should be 
placed in this phase and the armature current 
increased until the motor starts. Volts 
armature, amperes armature and induced 
volts field should be simultaneously read. 
The starting voltage is now held constant 
until the motor comes to synchronism, and 
the time required to reach this point recorded. 
The machine attains synchronism when the 
induced volts on the field fall to zero. The 
machine is then shut down and the t< 
are repeated for each of the other positions. 

If a motor shows a tendency to remain at 
half speed, the alternating current voltage 
should be increased until the motor breaks 
from half speed and comes up to synchronism, 
the voltage required t,i accomplish this being 
held until full speed is reached anil then 
recorded. 

If the test is required to be made with a 
compensator, the motor should be set with its 
field in the position where greatesl starting 
current is taken and allowed to rest in that 
position for at least six hours until the oil is 
well pressed "tit of the bearings. This is done 
in order to obtain the worsl starting condi- 
tions likely to occur in normal operation. 
Connections are then made to the lowest 
tap of the compensator, and with normal 
voltage held on the line the starting switch 
of the compensator is closed. If the motor 
fails to start, the voltage must at once be 
switched off and connections made with the 
next higher taps on the compensator, and so 
mi until the motor starts. Readings should 
be taken on each of the taps of the compen- 
sator in the starting position, with the machine 



TABLE XIV Starting Test on a 425 Kw., 11000 V., 8-Pole, 25-Cycle, 3 Phase Syn. Motor 















VOLTS LINE 






AMP. LINE 




per Spool 


Pos. at 

1 


Time to 




1-2 


2-3 


L480 


l 
15 


2 


3 


Syn. 


■ 




1430 


17..". 


15.2 


52 




Start 














2650 




:::, 




'.Hi. 7 






Syn. 










2650 


2650 


2650 


9.2 


9 


8.9 








Rest 














i:: 10 


15 


Hi 


la.ii 


-17 


2 




Start 












2560 






30 




ss ; 






Syn. 










6 


J" 


2560 


9.5 


9 : 


9.2 






70 Sec. 












1 1 .".. . 


1300 


i a l'ii 


15 


1 1 


12.7 


45 


3 


















2380 


29.5 






84.7 






Svn. 










2380 


2380 


2380 


10 


in. J 


10 






70 Sec. 












L248 


1260 


1165 


1.-, 


12.8 


13.8 


l I 


4 




Start 












2590 




33 






Sll.s 




68 Sec 


Svn. 








2590 


2590 


2590 


9 


9.3 


9.5 
















1 inn 


tans 




15 


13.9 


16.2 


49 


5 




Start 






2620 










32 


87 






Syn. 






2620 


2620 


2620 


s., 


0, 


9.3 






64 Sec. 



[s there any tendency to stiek at half speed? No. 



COMMERCIAL ELECTRICAL TESTING 



2IMI 



at rest, to determine the voltage ratio of 
the taps of the compensator. All these tests 
should be made with the field circuit of the 
motor open, and enough time allowed be- 



am *>o 

/SCO 90 

1600 ao 



1400 



70 



/ZOO ^60 

X ? 

%-/000 \jSO 

1; 800 \>40 

600 *30 



400 
ZOO 

c 



20 
/O 
O 



_,^^T X St "§- -s4-4- 


71 3 •$ a -js WY 


~7t3 Sk *** i§ +•* ** 


t? % i ^ 


T T l££- T 


A T * 


t - i^y- 


i + ,tp"K ^ 


it po-^r.it 


1 ^ -t^t 


t s 


S it 


->£ ~ 


^ 7 X- 


2* 


2 


^ 


y 



50 











/o 




20 




30 40 
Arrets. L/ne 






,5< 


7 






& 














































/ 


1 












































/ 




h 










































* 










40 


t— 


































/ 


^ 


1 










































, 


r 








































rS 


s 






1- 














■V 






i 










■<> 


,/ 


y. 




% 








$30 








_ 






1 








.N 
















^ 
























!J 






















17 






' 






























s 










































* M 




















* 














t 


(? 


y 






































c 

-- 


'p 










/J- 














C> i 


•e 


i. ■-'•, 


5 












— 
































— \— I 










s 


-' 


r- 






■+ 














- fv-/cC/or 


— +- 






4 


w 


v 


+ 


s 






- 






A) 















1 * 1 ' 


"T 


1 








1 


Hi 
Loc 


'c- 


Ll 


S. 









/o 



30 40 

Amps. Line 



60 



Fig. 37. 



Efficiency and Losses 011 a 1070 HP.. 13200 Vol,, 
3-Phase Synchronous Motor 



tween trials to permit the compensator to 
cool, since it is designed for intermittent 
service only. Table XIV. 

TABLE XV -Eft", and Losses of a 1070 H.P. 



Input-output efficiency test is made by the 
input-mil put method. 

Standard efficiencj tesl are made by the 
method of losses. In calculating efficiency, 
the same nomenclature is used as that 
employed for alternating current generators. 
C] is eitln-r taken from the phase character- 
istics or is calculated in the same manner a 
for alternating current generators. 

Watts input II'., = I'/.Q + iV'A'j. 
Walls output = II II ,- zW. 

Efficiency = ...'' 

ir = opcn circuit core loss corresponding 
to I'y. - < 7\ 1 'li the ci ire loss curve. 
II " 
Horse-power output = . 

See Table XV and Fig. 37. 

The non-inductive load heat run is madi 
as follows: Run the machine under load at 
unity [lower factor until it has reached 
constant temperature and record temper- 
atures. Take readings of regulation at normal 
and no load and full load phase character- 
istics. 

The non-inductive overload heat run con- 
sists in bringing the machine to normal load 
temperature, applying the overload for the 
specified time, recording temperatures and 
taking readings of regulation at unity power 
factor. 

Normal load power factor heat run is 
similar to the normal load non-inductive run, 
cxeepi that the machine is operated a 
specified power factor. Wattmeters should 
lie used as described for alternating current 

generators. 

Overload power factor heat run is similar 
to the overload non-inductive run, cxeepi 
that the power factor is less than unity. 

To bi 
13200 V., 6-Pole, 25-Cycle, 3-Phase Syn. Motor 



' r Load 


ii 


I'a 


:,n 


, 5 


100 


1 25 


150 


Volts Line 


13200 


13200 


13200 


13200 


13200 


13200 


13200 


Amps. Line 




9.5 


[9 ii 


28.5 


38 


i, .5 


.1, 


Amps. Flcl. 


50.1 


50.6 


51.0 


55.1 




63 8 




CR . . . 


— 


:;i ;, 


69.0 




168 


172 


205 


(V-CR) . 


13200 


1316 


13131 


13097 


13032 


13028 




Core Lo 


1900 


13800 


13 


13600 


1 :;.-,i in 




100 


\ Short < 'ir. ( ', iri 1. 


— 


17 


107 


190 


310 




7HII 


C*R Arm. 


— 


565 


2265 


.Mini 


90 i< 


nun 


20 


C 2 R Fid. . 




3630 


3680 


1300 


,050 


,770 


(171(1 


Friction 


6272 


6272 


6272 


6272 


6272 


6272 


6272 


Lo ses 


23722 


24314 


26024 


29462 


172 




1, 142 


K\v. Input 


23.72 


220.63 


136 


654, I 


870.1 


1089 




Kw. Output 


ii 


196 


H0.66 


624.8 


83 i 9 


1049 8 


1259.3 


H.P. Outpul 


ii 


263.2 


550 


837 


1121 


1 lll\ 




ficiency 


ii 


89.0 


94.4 


■ 




96.3 


96 i 


Res. Arm. I Line 1 3. 


B6 Ohms 25 


S ( 111,, 


Hot 47. 


Res. Fid. 




C. 1.4 


ms It 



210 



GENERAL ELECTRIC REVIEW 



A MOTOR OPERATED BILLET MILL. 



By B. E. Semple 



The Indiana Steel Company, Gary, Indiana, 
started its billet mill in August, 1909. This 
was th'' second of the several large motor- 




Fig. i. 



Last Two Stands of 40 in. Blooming Mill Shown in Foreground: Five 
Stands of 32 in. Blooming Mill in Background 



operated mills installed by this company for 
the manufacture of steel, that was put into 
regular i iperation. 

The principal work in this 
mill is accomplished by fh e 
i!.") cycle, :! phase, slip ring 
type induction motors, i he 
i if which are as 
Ei illows: 

'J motors, 1 | ii ili 'i || ii 
h.p.. 214 r.p.m., 6600 
volts. 

:; in 6000 

h.p., 83 r.p.m., 6600 Mills. 

These mi iii ir are de 
ed to carry full rated load 
continuously, with a I 
perature rise not in e: i 
■ it lOdegree < '. ; 25percen1 . 
overload continuously, with 
a ti mperature rise of not 
more than ."iii degrees ('.; 
and 50 per cenl . overload 
for one hour, with a tem- 
perature rise not in e: 
of 60 degrees ('. 

Like thi' rail mill motors described in the 
Review for Feb., 1910, they were purp 
designed for heavy rolling mill duty, their 



proportions being extremely liberal. The 
entire five motors represent a total weight of 
1518 tons, and will carry 'i'o times their 
rated load liefore dropping 
out of step. 

The method of connect- 
ing the motors to the rolls 
in this mill differs consider- 
ably from that employed 
in the rail mill, except in 
the case of the two 2000 h.p. 
motors, which differ only 
in that the gearing is 
located in the motor room 
instead of in themillpn 

The illustration on p 
L94 shows the east half of 
the south motor room, the 
two motors in the distance 
being the 2000 h.p. ma- 
chines which drive the hi 
in. blooming rolls. The 
motor in the fi ireground is 
a 6000 h.p. machine, and 
drives the five stands of 32 in. blooming rolls. 
each of which is connected to the motor driven 
shaft through bevel gears. 




Fig. 2. Primary and Secondary Control for 6000 H.P. Motor 



Fig. 1 is a view on the other side of the wall, 
showing in the left lore-round the last two 
stands of the 411 in. mill, and in the 



MOTOR OPERATED BILLET MILL 



2] 1 



background all five stands of the 32 in. mill; 
the former driven by the 20(10 h.p. n 
and the latter by the 6000 h.p. motor. 

The west half of the motor room contains 
another of the three 6000 h.p. motors. This 
motor operates the 24 in. 
mill, consisting of six stands 
of rolls, each connected 
to the motor driven shaft 
through bevel gears, and 
drives from one end only, 
instead of from both ends, 
as in the case of the first 
mentioned 6000 h.p. motor. 

Pig. 2 shows the primary 
and secondary control for 
the last named motor, the 
6600 volt motor-opera nd 
primary switch being locat- 
ed in the rear and to the 
left, and the secondary con- 
tactor panel in the front, 
with the secondary resist- 
ance directly behind it. The 
master controller is located 
to the left and in front, 
directly beneath the panel 
containing the instruments. 

In this mill the motors 
i artcd and stopped by 
the motor attendant rather 
than by the mill operators in the mill proper. 

Fig. :i is a view of the 18 in. mill, comprising 



the rolls are made thro 
bevel gears, as in the cases of the other 6000 
h.p. motors. 

Bach of the five motors is equipped with 
a heavy llv wheel to assist in smoothing out the 




„ .jp«. 1 1 ' 




Fig. 3. 18 in. Blooming Mill Operated by 6000 H.P Induction Motor 

five standi of rolls and driven by the third 
6000 h.p. motor, shown in Fig. I. The motor 
is located in the north mol ind the 



Fig. 4. 6000 H.P. ThreePhase Induction Motor 

peaks that would be demanded by the motors 
from the generating station if the fly wheels 
were not used. The wheels 
on the two 20HU h.p. 
motors are external, as 
seen in Fig. (i, while in the 
of the three 6000 h.p. 
motors. the additional 
weight necessary to obtain 

the desired fly wheel 
is addeil direct ly onto the 
ir. The fly u heel effect 
of the 0000 ' h.p. rot, ir is 
equal to 10 330,000 pounds, 
and that of the 2000 h.p. 
rotors, 1,720,000 pou 
at a one foot radius. 

The 2000 h.p. motors 
were assembled and ' 
at t he w l ni. oi the I iencr- 
al Electric ' he- 

id tin' fly 
wheels, which arc lamina! - 
ed. were a tembled at I he 

point of installation. Tin- 6000 h.p. motoi 
were entirely too large to ship, even partially 

'.led, and COn I '|llenllv Wl 



212 



GENERAL ELECTRIC REVIEW 



assembled at the Gary plant by experts sent 
from the Company's works. 

All of the motors have water-jacketed 
bearings, those for the 6000 h.p. being 30 in. 
in diameter and 70 in. long and those for the 
2000 h.p., 24 in. in diameter and 60 in. long. 
However, water is not used on the bearings 
excepting in instances of heating to such an 
extent as to demand it: owing, for instance, 
to the failure of the oiling system. 

This mill was designed to roll 4(10(1 tons 
in twenty-four hours and is the largest 
straightaway billet mill in existence; it is 
Strictly modern in every detail and its 
operation throughout has been entirely suc- 
ful. 

The rolling cycle begins with the receipt up- 
on the approach table to the first pass, of an 
8000 pound ingot from the reheating fun 
measuring 20 ft. by 21 ins. sq. section. 
Twenty-one passes arc made in reducing 



this ingot to either a 2 in. by 2 in., or a 1 3 4 in. 
by 1 3 4 in. billet. 

The first four passes are made in the 40 in. 
mill, driven by the two 2001) h.p. motors; 
the next five in the 32 in. mill, driven by a 
Conn h.p. motor; the next six in the 24 in. 
mill, driven by a 6000 h.p. motor; and the 
final six in the 18 in. mill, also driven by a 
6000 h.p. motor. 

The apparatus for controlling the five large 
motors in this mill is almost identical to that 
employed in the rail mill. Reversing switches 
are provided in order that the motors may be 
reversed if necessary, and provision has been 
made to introduce a predetermined amount 
of resistance into the secondary circuit to 
increase the slip and thus allow the fly wheel 
to share the load with the motor. 

The feeder circuits entering t His mill are 
protected against lightning and surges by 
aluminum cell arresters. 



THE ELEMENTS OF TRANSFORMER CONSTRUCTION 



Part 
By W. A. 



As already mentioned, the prime consider- 
ation in the lighting transformer is insulation, 
particularly between primary ami secondary. 
The material used at this point consists 
principally of a heavy layer of built-up mica. 
augmented by high grade material carrying 
varnished film, which i thi besl insul- 

ators. There is thus afforded a certain pro- 
tection, nnt only under normal conditions, but 
also under those of severe overload, short 
circuit, or external tire, which may com- 
pletely disintegrate the internal transformer 
the windings come together and thus 
allow the high potential of the primary to 
pass to the secondary line, with possibly 
Serioil uences. While the transformers 

arc designed for operation at 2 loo volts or 
they are regularh tested by the manu- 
facturer, between primar;, . ndar\ . at 
no1 less than ten thousand volts, the aver- 
age breakdown strength being probably more 
than double that amount. 'I insulation 
between turns, layers, sections and coils are 
generally fibrous, untreated materials, par- 
ticularly adapted to receive and retain the 
oil-proof insulating compound which is ap- 
plii d by high pressure to the coils after they 



Errata: April Rbview, page 1--' n. line 14. 

read Figs. 3. 4 and olumn, ."»th Hi 

" ro, should read Fik. 4. 



II 

11 \1 I 

have been subjected to vacuum and which 
permeates the innermost fibres and interstices, 
forming a compact structure. This serves to 
preserve, protect, insulate and conduct away 
tin- heat generated within during opera 
Tlie otherwise spongy mass of wire and insu- 
lation is thus also made capable of resisting 
the mechanical stresses. Pig. 11 shows a 
group of transformers finished and ready for 
test. An interesting comparison with the 
design of a quarter of a century may be 
had by referring to Fig. 10, which shows on, ,. 
the first commercial transformers made in 
this country. 

Next in importance arc durability, reliabil- 
ity and longevity, to insure continuity of 
service and low rate 
i >i depreciation. These 
features demand su- 
io] insulation and 
mechanical construc- 

and mod. 
temperatures, the lat- 
ter with particular 
reference to an even 
distribution thereof. 
It is now common 

1 'fact ice to make the case tighl and fill it 
with a specially prepared oil, completely 
submerging the transformer. In operation, 
'he heat starts a natural circulation upward 




Fig. 10. Transformer of 
Quarter Century Ago 



ELEMENTS OF TRANSFl IRMEF CI INSTRUCT!! IN 



213 



in the center, from the warm transformer 
outward to the sides of the cast- at the top, and 
thence by contact with the cooler sides of tin- 
case downward to the bottom, when it is cooled 
ready for return through the transformer. 
In addition to its cooling properties, the oil 
possesses a very high insulating quality, and 
in consideration is practically indispensable. 
Small masses of coil must be opened by 
ventilating channels which will direct the oil 
to their innermost parts in the course of its 
circulation; while the larger masses must In- 
subdivided into several coils interspersed by 



as follows: These transformers are built 
in sixteen standard sizes ranging from 
6 Id kw. to 50 kw., the average of all trans- 
formers built being about 7'-j, although as is 
evident, sizes smaller than this predominate 
in number. These small units are installed 
on lighting circuits in vast numbers, and their 
use is at present increasing at the rate of more 
than 50,000 per annum. These circuits are 
excited continuously night and day at normal 
voltage, and since the core loss of the trans- 
former is dependent only upon the vol!;, 
the system, it is constant for all loads on the 




Fig. 11. Group of Small Transformers Completed and Ready for Test 



generous channels which will give the cooling 
medium access to parts alike, thus main- 
taining uniform low temperatures. 

The primary wires of small transformers, 
which are of very small cross-section, art- 
round, all other conductor bein 

gular section. The latter improve the 
factor and afford ample hearing surfac 
resist crushing of insulation through mech- 
inical si resse . and operal • in conjunctioi 
with the coil filler to produci olidi 

coil of e\ en temperature I > prevent un 
expansion and contraction. These pre- 
cautions, well executed, insure reliability 
li 'Hi' sen ice. 
ely follow ing the e qualities in impor- 
efficiency. A coi ideration of 
this factor must take account of a somewhat 
■niM nal condition, which may be iummed up 



transformer, including no load. The copper 

qu ire < if t he load, an 
ordinary service is considered to be 
equivalent to that corresponding to full load 
for three hour-., for each daw From this 
fad alone, the ratio of these two losses in a 

designed transformer might be expected 

i" be one to eighl . li however, 

o t of supplying the energy for the two 
purposes is not equal. The core li 

ained largel . dui 

when a minimum. < In 

ither hand, the copper loss is largely 

carried at a time when the station is operating 

. bul when it is frequently 

Ml .pl th i and 

the 
outpul It wi iuld bi difficult to lix I 

of supplying this waste energy, bul the 



214 



GENERAL ELECTRIC REVIEW 



mean of a number of values obtained from 
many of the large stations places it at 1 cent 
per kilowatt hour for core loss and 4 cem 
kilowatt hour for copper loss; whence, in 
consideration of the time during which each 
is maintained, the relative costs are as 2:1. 
In designing the transformer, other factors 
enter to distort this relation. With existing 
materials, cost of labor and present practice, 
it costs more, generally speaking, to produce a 
transformer with low core loss than one with 
low copper loss. Coincident with high core 
loss is likely to be high magnetizing current, 
which is detrimental to satisfactory operation. 
( (pposed to this, however, is the fact that the 



sizes having a relation varying along a smooth 
curve between these extremes. The full load 
efficiencies vary from 95 per cent, on the 
smallest to 98.5 per cent, on the largest sizes, 
disclosing the fact that these small pieces of 
apparatus, without moving parts, transform 
energy at a very high efficiency. 

A multiple transformer must not only 
operate continuously with good efficiency, 
but at the same time must maintain a con- 
stant potential on the secondary lines at all 
loads within rating. In other words, jits 
regulation (defined as the per cent, of second- 
ary voltage variation from no load to full 
load) must be very low. The principal 




Fig. 12. General View of Winding and Clamping 

regulation -another measure of meril varies 
substantially in direel proportion to the cop- 
per loss and should l)c kepi low. Likewise, 
the temperature during operation depends 
primarily upon the copper loss and demands 
a small value. Core li i also affects temper- 
atures somewhat, although to a less degree 
than the copper loss, owing to more ready 
means of dissipation. 

A compromise between these many depend- 
ent variables of manufacture and operation, 
as well as '"i of depreciation, interest on 
investment, and other fixed charges, has 
resulted in a design which gives substan- 
tially equal losses in the smallest sizes, and 
in the la izes a copper loss twice that 

of the core loss; the lo i o the intermedia 



Pancake Co-Is for Large Shell Type Transformers 

factor affecting regulation is the voltage loss 
caused by the ohmic resistance of the copper, 
commonly termed the I R drop. In fact, the 
other principal component, reactive drop, 
need not be considered in approximations, 
except under special conditions of load 
involving low power factors. Since the IR 
drop bears the same relation to the normal 
voltage that the copper loss docs to the 
transformer capacity, the regulation of a 
transformer may be estimated with a fair 

degree of aeeuraey by dividing the CO] 

loss by the capacity of the transformer, both 
expressed in the same units. The actual 
regulation can newer be better than this. 
in fact, it will lie usually about 5 per cent, 
higher. 



ELEMENTS OF TRANSF* iRMER COX STRUCT K >.\ 



■_' 1 5 



Now the evolution from this lighting 
transformer to others in this group consists 
merely in magnitude of figures and the 
accentuation of certain characteristics, due 
to either the physical proportions or a change 
in the demands of service for which it is 
intended. The same fundamental factors 
enter into the design and construction of each. 
although their relative importance is modified. 
For example, the output of transformers is 
approximately proportional to their weights, 
or masses; the losses, therefore, are also 
proportional to this factor. The only means 
of dissipating these losses, however, is in form 
of heat, through the surfaces of the trans- 



En like maimer the mechanical strain, 
which is always exerted in a transform 
the resultant of the magnetic forces, and 
which tends to tear asunder turns, coils and 
con is quite insignificant in the small 
transformer protected by its relatively large 
surface and compact form; but in the 
power transformers, this item demands most 
careful consideration from the designer. 
Think for a moment of the possibilities for 
damage when 10,000 kw. — approximately 
13,500 h.p.- -is suddenly short circuited on a 
transformer, and it will not be surprising 
to know that solid coils well constructed and 
carefully supported on extensive bearing 




Fig. 13. Removing Shell Type Coils from the Baking Oven in Insulation Department 



formers. That is, the losses or heal uni 
be dissipated im n the cube of the 

linear dimension, whereas the surfaces in- 
crease only as the square. Obviously, 
if the same temperature of operation i to be 
maintained, a different mean, to the accom- 
plishment of thai end mu t be introduced as 
ilie unit grows larger. Here, then, i oni 
characteristic which, while negligible in a 6 10 
kw. transformer, requii channi I . 

then more, and finally artificial ling in the 

form of air-blasl . forced oil irculatii t 
water-cooling coils immersed in oil, a 
size of the unit increa 



surfaces crush under the enormous pressure 
dei eloped. 

Efficiency and regulation, o important in 
Mi, mall lighting transformer, become oi 
relatively minor importance. This cla 
apparatus operate continuou ly upon ti 

mission Mir . | he load upon which van- 
less than that upon the small lighting tl 
former, or one opi ill motor load. 

[\hi on drop ■ uch a 

arativel) narrow ran can be 

- irrected bj taps in the win Lin 

which the ratio of " 

hanged. 



216 



GENERAL ELECTRIC REVIEW 



Again, the position of these large units on 
long transmission lines, which are subject to 
sudden excessive rises of potential from either 
lightning or line disturbances, makes it neces- 
sary to strengthen the ends of the windings 
by supplementary insulation of a very high 
value; while rushes of current from short 
circuits must be minimized by an amount of 
reactance in the design consistent with the 
best interests of all considerations. 

All these requirements, for reasons already 
cited, have led to the almost universal adop- 
tion of the shell type for such sen-ice. The 
air-blast and water-cooled types are con- 
structed much the same fundamentally, 



ings, the primary and secondary being inter- 
mixed and the whole interspersed by suitable 
barriers of insulating collars. The various 
groups are effectively encased in a box-like 
structure which, while serving as an electrical 
and mechanical protection, is so arranged that 
it will not obstruct the oil channels which are 
found adjacent to every coil. 

These windings are then set up vertically 
in the bottom frame and the magnetic circuit 
built around them in the form of rectangular 
sheets of steel (Fig. 15). The top frame is 
next added and securely clamped to the bot- 
tom, compressing and securing the core. After 
connection board, leads, etc., are added, the 




Fig. 14. Assembling Coils for Large Shell Type Transformers 



although they differ materially in details and 
external nee. The C( >ils. both primary 

and secondary, are wound in the so-called 

icake type Fig. L2); i.e., they employ 
Hat rectangular wire and are wound one turn 
per layer, in many layers, forming a spiral, 
the insulation between turns consisting 
Hi' paper, mica or varnished cambric, or 
all three together, as conditions demand. 

These thin coils . ted with coil filler 

and wound with a number of layers of tape. 
depending upon the voltage for which they 
are designed, each layer being given several 
coats of insulating varnish, baked on (Fig. 13 . 
These coils are then assembled into groups 
(Fig. 1-L and the groups into complete wind- 



transformer is ready for its casing. If of an 
air-blast design, the casing is arranged to form 
a blower, receiving air at its base through 
a conduit in the floor. The circulation is 
through channels about the coils and iron, 
the air gaining acci to all parts and convey- 
ing heat out through the discharge at top of 
casing. 

If the transformer is designed for water- 
cooling, it is hung to a heavj east-iron cover 
or cap fitting on a tank of boiler steel, and a 
coil of water pipe placed around it near the 
to].. The whole is then lowered into position 
in the tank, [n operation, these water coils, 
which are located in the upper or warmer 
strata of oil. cool the oil so that it falls along 



ELEMENTS OF TRANSFORMER CONSTRUCTION 



21< 



the outside, near the walls of the tank, aiding 
the natural circulation to the extent that all 
parts are kept at a substantially uniform 
temperature. 

The air-blast type is used for moderate 
voltages where cooling water is expensive or 
unavailable, and has been built for voltages 
up to 35,000, in sizes up to 5000 kw. The 
water-cooled type, which is 1 utter adapted 
f< ir high potentials by reason of its superior 
facilities for insulation afforded by oil im- 
mersion, has been constructed for voltages up 
to 140,000 and capacities up to 10,000 kw. 
The general construction of this interesting 
class of apparatus is shown in Fig. 10. 

Between these two divisions of the multiple 
transformers, falls a class of moderate capacity 
and wide range in voltage. This class demands 
many turns of small wire and generally follows 
the core type in design. The units of this 
class are nearly always installed in buildings 
or sub-stations where power is generated or 
received and transformed for testing, for mill 
work, or for supplying rotary converters for 




Fig 15. 



Building Up the Core of a Large 
Shell Type Transformer 



ay work 'I'll from the lighting 

transformer only in that, b< e ol capacity 

and voltage, they require a g > ub 

division of coils, the propei supporting of 
h demand i a more c rniplii ted • ■ 
tructure. Fig. 17 shows a representative 
type of this division. 



This class of multiple transformers is 
completed by a multiplicity of miscellaneous 
styles to which this pa m onl} briefly 

refer, such as sign-lighting, individual incan- 
descent lamp, tele]. In. ne Hue insulating, bell- 




Fig. 16. Transparent View of 2000 Kw. 
Water Cooled Transformer 

ringing, wireli aph, signal, instrument 

or switchboard, and railway transformers. 

The wireless and signal transformers are 
examples of designs employing active 
11 nuts other than Steel and copper; t he former, 
intended for very high frequencies, substitu- 

i el in ' he core, w hile t he 1 
for certain rea ons, is wound with high 
ce wire. 
The prime function of the multiple tri 
formers so far described, is to transform 
electrii al energy at a fixed ratio of volt: 
and i hal of th< erii transfi n mer now to be 
con idered is to make the transformation al a 

fixed ratio of currents. Tl 

a matter of fact, perform both of 
i 

the two i 
ampL . in t he multiple tran former, anj 
current in magnetizing the con' is 
only so 
regulation or the powi of the circuil 

I in the ol her hand, 
i his nature in a 
transforms ihibitive. Conversely, the 



21S 



GENERAL ELECTRIC REVIEW 



voltage loss in a series transformer is of 
importance only so far as it affects the 
current regulation, while in the multiple 
transformer, it is of the greatest moment. 




Fig. 17. High Voltage Core Type Transformer for 
Power and Testing Purposes, 

By far the most common form of the series 
Lpparatus is thai generally styled 
"currenl transformers." These transformers 
are mounted on the framework of switch- 
boards and introduced into a main bus or 
feeder as a multiplier and insulator for the 
instruments that measure the current or 
power in the feeder, or to operate the pro- 
tective devices which open the switches in 
emergencies. Their use with meters measur- 
ing large amounts of power delivered to a 
distributing company or large consumer im- 
mediately suggests the necessity of a refinement 
in accuracy, not required or attainable in the 
i irdinary transformer. 

They are called upon to deliver but a 
raction of a horse-power; yet, controlling 
the protective devices, they are by far 
the mosl important elements in the struc- 
ture, assuming a prominence ou1 of all 
proportion to size i i The ratio of test 

to operating voltage is. on this account, gener- 
ally three instead of two as U I rans- 
formers. Considering the remarks made in 
irly part of this paper concerning space 
factor and its (■fleet upon efficiency, it may 
be rightly inferred that the additional insu- 



lation necessary imposes a serious obstacle to 
accuracy, especially in those transformers 
that have been built for circuits of 110,000 
volts. Fig. IS, which shows a transformer 
constructed for this voltage, is impressive 
when the 40 watt output is contrasted with 
the total height of about 9 feet. 

Up to the present time, the best trans- 
formers of this class have been made on 
either a ring core without joints, or of a shell- 
type design, with joints in the magnetic 
circuit. The former economizes material at 
the expense of labor, particularly in winding, 
where the wire is threaded through the center 
of the ring — a laborious process for skilled 
labor. The latter design, necessarily demand- 
ing lower magnetic densities and consequently 
more material to compensate for the detri- 




Fig. 18. Current Transformer for 110.000 Volt Circuit 

mental effect of the joint in the circuit upon 
accuracy, is less expensive in labor as the 
coils may be machine wound and subse 
quently assembled. 

The only other examples of this class of 
transformers requiring mention here are those 
used in compounding self-excited generators, 
and those inserted in series lighting circuits 



ELEMENTS OF TRANSFORMER CONSTRUCTION 



219 



carrying arc or incandescent lamps of a certain 
current rating, for the purpose of operating 
a local circuit carrying series lamps of tin- 
same or different type but of different current 
capacity. The first of these is inserted in the 
line from the generator and transforms a 
portion of the current, which is then rectified 
to direct current and sent through the field 
coils of the machine. Neither requires the 
extreme accuracy of the switchboard or 
current transformer, although the capacities 
are much larger and operating voltages 
moderately high. In construction and ap- 
pearance, they resemble small multiple trans- 
formers. 

Thus far we have considered transformers 
with stationary parts and fixed character- 
istics. We now come to the third general 
class of apparatus, in which, by means of 
moving parts, a combination of the properties 
of the two previous groups is acquired. The 
constant current transformer, by which 
name this third class is usually known, is 
made upon a long slender shell-type core with 
pancake coils. In the simplest form, there 
is one primary and one secondary coil, 
occupying not more than a quarter of the 
length of the core window. The primary is 
fixed at the lower end of this space by means 
of a suitable clamping device attached to the 
core clamps.* The secondary is hung by 
flexible cables to rocker arms and counter- 
balanced by weights, so that it is free to move 
throughout the length of the window; al- 
though it naturally rests upon the secondary 
because heavier than the counter weight. 
The primary is connected in multiple with 
the line supplying energy, and the secondary 
in series with the lighting line of cries arc or 
incandescent lamps. 

If the coils are separated as far as possible 
and the circuit closed, the magnetic field 
established by the primary is opposed by 
that of the secondary, and the coils are 
Eorced apart by this electromagnetic force. 
Mo i of the lines of force are driven back and 
cro the windows, or "leak" to the outer 
legs, while a small portion threads the 
secondary, producing voltage and currenl 
in the line. Now, if th< counter weight is 
lessened, the weight of the coil causes n to 

overcome the repulsion and to settle nearer the 

primary, embracing more flux and then 
developing more current and voltage and re 
during the reactive or leakage I ix. By a suit- 
able adjustmenl of the weights, any current 
value within the limits of the design may be 



obtained. The number of lamps on the line 
may vary at will, demanding more or less 
voltage, but the coil will always float upon 
the leakage flux, threading enough to give 
the voltage necessary to maintain constant 
current on the secondary lines. This action is 
not unlike that of a floating body, which 
always displaces its own weight, regardless 
of the specific gravity or density of the 
supporting medium. 

The fourth or final group, as we have 
classified them, broadly designated regu- 
lators, performs a function quite similar to 
that of the apparatus just considered, but in 
a different manner. The secondary voltage 
rather than the current is the factor regu 
lated, although the same apparatus may lie 
adjusted to control current under certain 
special conditions of load. 

The principal purpose of these devices is to 
receive a voltage which, although nominally 
of constant value, nevertheless varies exces- 
sively, due to poor regulation of generating 
and distributing apparatus under heavy or 
changing loads, and convert this into one of 
constant value. They are generally installed 
in a generating or sub-station, on feeders 
supplying energy to the centers of heaviest 
load upon the system, that the proper vol- 
tage may be maintained at these important 
points. 

These "feeder regulators," as the} 

nonly called, arc designed in two general 
types, both of which are made lor either hand 
or automatic control. The simpler form of 
this device consists of either a core-type or 
shell-type transformer, the secondary of 
which is subdivided into several equal coils 
successively cut in or ottt of circuit by means 
of a switch. The other, or induction type, i 
in reality a generator of special design, in 
which the rotor is connected in multiple with 
tlie primary line, and the Stator in series with 
i In feeder.* 

lnconclusion.it should lie observed thai 
this paper presents only a very general view 
of transforming apparat us, dwelling rcl.it i\ el\ 
upon the salient points of the prevalent type, 
the multiple transformer. Again let it be 
pointed out that all of the other classes, types 
and form possess inherently the same char- 
acterisl ics of de ign and i iperation, which 
differ only in relal ive importam tiding 

upon the requirement of the service for which 
they are intended. 

*Stn i I ' Mil the 

I 



220 



GENERAL ELECTRIC REVIEW 



HYPERBOLIC FUNCTIONS AND THEIR APPLICATION 
TO TRANSMISSION LINE PROBLEMS 

Part II 
By W. E. .Miller 



Sign Convention 

The positive direction of rotation has been 
taken as contra-clockwise, as this is the 
convention usually employed in mathematics 
including trigonometry. Steinmetz uses the 



*-e 




opposite notation which has advantages also. 
In the clockwise rotation impedance is 
written r—jx; in the contra-clockwise rotation 
it is written r+jx. 

A leading current is represented in the 
contra-clockwise notation, i = a+jb; a—jb 
lagging current, jb being drawn 
downwards as shown in Fig. 5. 

Y 




Fig. 6 

y If a vector is multiplied by j, it rota 
contra-clockwise through one right a 
For instance, if tfo a ±jb is multiplied 

by j, the result is jaTb, which means that <i 
has tv orward through one right angle 

and b also, which now lies in the op] 

ion to the original din of a. If a 

further multiplication by j is performed, the 
result is —aTjb and the vector has been 

ed into tin- third quadrant, and 
Similarly, multiplying by — j rotates the 
vector clockwise or in the negative direi 

Sic Pig. 6. 

Forms Used for Complex 

The complex a+jb is often written \ ./ 
| _* where = t>m ( I. A 



Anothei ormin which 



the complex is written i \ 
this form being immediately obtained from 
ction of Fig. 5. This method of writing 



the complex is very useful in many cases, 
for instance, when it is required to write down 
the complex of a current which lags or leads a 
voltage taken as the standard phase, and the 
power factor is given. In this case, i = \ a- + lr 
(PFT j v l-PF 2 ). For example, if the power 
factor is .90 lagging and the R.M.S. current 



is 120 
= 108- 



amperes, 
52.3/. 



then i = 120 (.90 -jV .19) 



Meaning of \/<J -\-jb 

The value of this quantity is required later, 
hence, the following method is given to show 
how to extract its square root : 

Let \ a+jb=c+jd then a+jb=c* — d*+2jcd 

Then, since the real parts must be equal to 
one another, and also the unreal, 

a =,---</- and b = 2cd, hence <-+</- = \ a' + b- 
Now c+jd= \ c-+d-(cos e'+jsin 8 1 ) where 6' 

■ X)_ 

And a+jb =\ a'+b 1 (cos 0+j sin 9 

(b\ b 

) ' ; » "=a 





=to« 12 


6 

a 

9' 




2( d 


= 


d 

■> 
<~ 

d'- 


L> l,i n 

1 -tan 


19' 
s 0' 


fore fl 1 


= 


« 
2 


hence, 


as 


c+jd = \ c"+d : 


iL 












>i - 


la n 
6 


() 





it follows that's ,i+jh = (a-+b') 1 

or \ " +jb 
= (a 1 +b*) 



X) 



( 



tan ( ') Ian (-) 

-A?! +j sin y> 



) 






Hence, the rule is as follows: Find the 
fourth root of the sum of the squares of <; and 

b. Find the value of the angle whose tangent 

is , then halve it and find the cosine and sine 

a 
of half the angle. If this angle is ,.', the 
resulting complex can be written 

• [cos './' ■*"< *] 






LONG DISTANCE TRANSMISSION LINE PROBLEMS 

Therefore cosh (x+_jy) =cosh x cos y± 



221 



If the original complex was \/jb—a, the 

angle whose tangent is I -- - 1 lies in l Ik- second 

quadrant, halving it, however, brings it back 
into the first quadrant, where the sine and 
cosine are both positive. Hence, vj'A - a 
must have the positive sign placed between 
its components. Similar rules apply for any 
root, and in general 
"Va~+Tb 



j sinh x sin v 



(17) 



= (a-+V-y> 



( 



to. 



— - +j sin - - 



) 



Division by Complex 

If the value of , "., is required, multiply both 
c+jd 

numerator and denominator by c—jd; then 
a +jb _ (a +jb) (c —jd) _ ac + bd+j(bc —ad) 
c+jd ' (7+jdJ{c -jd) ~ \-d* 

which eliminattes the j term from the denom- 
inator and brings the result into the form 
p-\-jg. If the denominator had been c—jd, 
the multiplier should, of course, be c+jd in 
order to clear the denominator of terms 
involving j. 

The following example is given here show- 
ing the application of this rule. Take the 
ordinary equation connecting volts and amp- 
eres in an inductive circuit 

di 
v = ri+L-r , i being equal to / sin j>l where f> = 2ir/. 

Then this equation can be written v=ri+jLpi or 

i = 



ji _ r —jLp 

r+jLp ~"''r- + L-p- 



which immediately solves the problem and sho 
that the current lags behind the c.m.f. by an angle 

tan — • 



Hyperbolic Complex 

These functions are involved in the solution 
of transmission line problems (with distrib- 
uted capacity, self induction and leakage). 
They appear in the form cosh (x+jy) and 
sinh (.v + /'vi. 

By the addition and subtraction formulae 
'14 and L5) which must apply generally, the 
following formulae are a1 once obtained: 

cosh (xj-jy) =cosh x cosjy±sinh x sinjy and 
sink t\±jy) =sinh x cosjy±cosh > sinjy 



Now cosjy = 1 + 






hel -1-TT+jT 



— etc. 



-■cosy 



Proceeding in a similar manner sinjy 

formula- 12 and L3) 



and sink <x+_jy) =sinh x cos y+jcosh x sin y i 18) 

from which formulae the hyperbolic complexes have 
been calculated. 

Thus if cosh (x+jy) =a+jb and sink (x+jy) 
= c+jd 

Then a =coshx cosy and b =sinhx siny 
c =sinhx cosy and d =*coshx siny 

Equations (17 and 18) show that coshu .md sinhu 
are periodic with an imaginary period of 2xj, since 
cosh iii+2-n-j) = coshu ins 2jt+j sinhu sin 2ir = cosh u 

Similarly sinh (u+2irj) =sinhu. These functions 
change sign when it is increased by jv « 
cosh (ti+j*) = —coshu, and similarly for sinhu. 

Again by substitution in the addition formulae, 
the following holds 

cosh I u -{■—!= jsinhu and sinh I**"f""o" J = jcoshu 
j sinhu and sinh I u 4—^- I 



also cosh I u +-4" ) = 
= —jcoshu. 



If it is necessary, as in long telephone lines. 
to calculate the hyperbolic functions in which 

the j term is greater than - , a great saving in 

labor can be effected by using the above 
results. For example, 

i osh I a I 2.57 j) =j sinh I " + I 2.57 - ., I j I 

- j sinh (k + 1.0 j) 

cosh {u t 3. 12 f) ■■ cosh [u -, (3.42-tt) j] 
= -cosh (w+.28 j) 



u+6.Q0j) = -.;' sinh u+f&.OO "*\i 






= -j suihti< + L.29 j) 

cosh (a +7.00 j) =cosh [u I (7.00-2ir) j] 
= cosh (« + .72 j I 

Similar formulae hold for sinh [u \-jv) 

The real pari of the complex cannot . how- 
ever, be reduced, only the unreal or j 
Hi nee, if large values ol the real term i 
are required, they must be calculated Ei 

. if no tallies are available, or from the 
exponential values of the hyperboli 

Transmission Line Equations 

Lei r re i tance per mile, L = self induction 
per mile n utral, 

C = capa<it y per n ; between line 

and neutral, and g= coefficient of dieli 



222 



GENERAL ELECTRIC REVIEW 



conductance per mile. Let x be the distance 
to any point of the line measured from the 
receiving end in miles, e the voltage at any 
point, and i the current. Then the following 
equations give the relations between "e" 
and •■/": 



di n de 

Tx =ge+C d7 



(19) 



provided that the value of g is independent of the 

orona effect : or pro- 
vided that the voltage is practically constant 

the line. 
And 



de di 

Tx =ri + L Tt 



(20) 



That is to say, the increment of current at 
any point per infinitely small length equals 
the vector sum of the leakage current (or the 
leakage conductance multiplied by the volts 
at that point) and the capacity current, which 
is at right angles to the leakage current. In 
the same way, the increment of voltage at 
any point per infinitely small length, equals 
the volts consumed in resistance added 
vectorially to the inductive volts at right 
angles to the resistance volts. 

de de 

Now C . - =jpCe since -jT'S at right angles to e 

... i/; ... . di . 
And L - =jpl.i. since -r- is at right angles to ; 

Where [> = 2*-/ 

Therefore, ^ = (g +jpC)e and j- = (r+jpL)i 






Whence, — = ( r +jpL) (g+.j; 



(21) 



22 



Hence, the solution is hyperbolic, because 
in both equations, the second differential is 
proportional to the quantity itself, a law 
which mini and coshu both follow. 

Then fo itionis: 

e = .\ cosh mx + B sinh mx 

i = /• ,„\h mx •-!> sinh mx, of which only 
two i ■' ■.nits are arbitrary. 

And m-' = (r +.,>/. i (g-f 

If the receiving end terminal values of c and I be 

I 



e = E r cosh m.v-r-m, /, sinh mx 

E. 
i = / r cosh mx+- '- sinh mx 

m, 



23) 



Where .v = distance in miles, measured from the 
receiving end, and 



Mg — jpC) 

" !l = „*j-Jr" and 
g- + p-C - 



J_ = g+ipc 

iii i m 



If E s and I s are given at the sending end, and 
the line is measured from that point towards the 
receiving end, equations 23 and 24 become 



e = Bt cosh mx — nti Is sinh mx 



I =I S cosh mx sinh mx 

Wl 



(25) 
26) 



Where .v is the distance in miles measured from the 
sending end. 

Calculation of Constants 

As already stated, ni- = (r +jpL) (g+jpC) 

In the majority of lines, except those 
using wires of small diameter at vcr\ high 
voltage, where corona effect is noticeable, g, 
the leakage conductance, can be neglected. 

Then, m- = (r+jpL) jpC = pC ( jr - pL 



Therefore, m = \ ' pC (r--{-p-L 



' tan ( — I 



= \ / pC(r*+p-L-)' 



( 



tan ( -Vl 
\PLJ 



+j sin 



U) 



) 



(27) 



The above is. of course, of the form a -{-jh = m 

rn {fi 'l = b . _ - 7 '" 

jpC pC ' pC 

pC pCib+ja) 



Since m, 



m, b-ju b"-+a- 

The tables for m, 



(28) 



m, 



1 



and — , in the 

in, 

Supplement have been calculated from thi 
formula', C being given in farads per mile 
and I. in Henrys per mile. 

Volt and Current Phase Shift and Power 
Propagation Velocity 

Equations 23 and L' 1 prove that when 
there is no load current, there is a complete 
reversal of phase in volts and amperes along 

a transmission line in a distance x - , where 

(a+jb) = m because both sinhtnx and coskmx 
change sign every half period -j. In a distance 






LONG DISTANCE TRANSMISSION LINE PROBLEMS 






v = 



2- 

-r- the amperes and volts are in the same 

phase respectively as they are at the 
receiving end. Hence, if the frequency 
be /, then the velocity of propagation of the 
voltage or current wave along the line will be 

b - 

This must not be taken as the velocity of 
the power wave along the line, as the apparent 
velocity of the current and volt wave vary at 
different points from the receiving end and 
the shift of phase does not vary uniformly 
along the line, owing to capacity current, 
the current leading the volt wave 90 degrees 
at the receiving end. If a lagging load 
current, however, is taken at the receiving 
end, the power factor can be approximately 
unity along the line, in which case the volts 
and current are nearly in phase at every point 
and the velocity of either gives the velocity 
of the power wave along the line. In the 
majority of lines used for long distance work, 
the resistance is not large enough to affect 
the velocity and in such cases the velocity 
of power propagation is practically equal to 
the velocity of light. For r = o, the velocity 



2-/ 



1 



P\ LC VLC 
or independent of the frequency. From this 
formula, the formula for the natural period of 
a transmission line can be derived equal to 

, , — where / is the length of the line ; — 
4/\ LC \ LC 

being the velocity of light nearly, the ex- 
pression only representing the velocity of 
light when the self induction inside the wires 
is negligible, which is true of very high 
frequencies, practically perfect conductors, 
etc. The natural frequency of the funda- 
mental wave, for a transmission Hue inn miles 
long is about 115, the velocit; of power 
propagation being approximately, l.S per 
cent, less than the velocity of light. The closer 
the wires are together or the larger they are, 
the slower does the power travel, and the 
velocity can be taken as lying between 
1 ."> and 2..") per cent, less than the velocity 
of light. For transmission lines, 184,000 
miles per second can be taken, as an average 
icity. 
It must be remembered that oower is a 
double frequency quantity and cannot, there- 
fore, be represented vectoriallv in the same 
plane as a vector of different frequency; 



hence, if the power wave is obtained by 
multiplying the complexes of current and 
volts together, difficulties are encountered. 
The best way to obtain the electric power is 
to plot the instantaneous values of the 
current and volts along the line, the values 
of which are immediately given by equations 
23 and 24. Then multiply the insta 
values together and plot the power curve 
from the result. The distance between the 
maxima, minima, or corresponding ; 
on this curve multiplied by double the Inn 
frequency gives the velocity of power propa- 
gation along tin' line; the distance between 
the maxima on this curve will, of course, 
be half that between the maxima on the 
current or volt curve, provided that practi- 
cally unity power factor obtains through 
the distance taken. 

The shift of phase of volts or amperes 
along commercial transmission lines is not 
large, since the maximum frequency used is 
only 60 cycles and with this frequency the 
half period length is about L500 miles. In 
long telephone lines, on the contrary, shift 
of phase is very large and will amount to a 
number of complete reversals along the line 
owing to the necessarily high frequency used 
in speech, S00 per second being a represen- 
tative frequency. 

Approximate Formula; for Short Lines 



Since cosh a 

for small values of u 

i 
cosh u = 1 + ■ 



U- M* 

1+F2+ . " 



nearly 



Similarly sinh u = u nearly. 
Hence for shorl line, if mx = xif> 



£,( 1 + 



and 



< 



x-ip--q-l 



+./'*>/ 



£+*»*) 



■ m,I,<f 1 ' 

• iq 2 i 

»h 



x-ip'--q-) 



+ ix-pq )-mJs(.p + i< 



I A 1 + 






+ /'.v'->/ 



) 



5 



These formuhe are accurate to 1 per cent. 
for lines, L20 miles long at 60 cycles and 150 
miles long at 25 uracy 

bein < ibtained for shorter line 

Corona Effect 

The escape of electricity through the 

atmosphere from one wire of a transmission 

line to another is an example of the increase 

of conductivity of a gas due to high dielectric 

The conductivity is enor- 



224 



GENERAL ELECTRIC REVIEW 



mously augmented under special conditions; 
such as, when subjected to radio activity, 
when the temperature is raised above a 
certain value, when drawn from the neighbor- 
hood of Barnes or electric arcs, or after being 
in contact with incandescent metals or carbon, 
etc. A gas through which an electric dis- 
charge 1 is passing is also affected in a similar 
manner, this being the cause of the increase 
in conductivity of the air between trans- 
mission lines when the voltage rises above a 
certain critical value. The physical asped 
of these phenomena has been studied by 
many scientists, notably by Kelvin, J. J. 
Thomson, Rutherford, Hittorf, etc., and a 
very full discussion of the whole matter has 
been given in Thomson's work "Conduction 
oi Electricity Through Cases." 

According to one of the modern theorii ol 
matter, each atom or molecule is composed of 
or associated with negative and positive ions 
or minute electrified particles, the negative 
ion po i ing a mass small compared to 
that of the hydrogen atom, and the positive 
ion a larger mass than that of the negative 
ion. The electric charge of these ions is a 
nit. On this assumption, the following 
di cussion may help to picture what happens 
when the voltage stress is increased in 
the dielectric between two conductors, beyond 
the dielectric strength and the gas becomes 
ionized. It can, however, only be regarded 
as a rough approximation to the phenomena. 

Capacity Current 

Suppose thai a potential difference is 
iplied to two electrodes separated by 
an air space, the potential being gradually 
ised. At first, the current passing 
the air, which co es the electric 

circuit, is exceedingly small and consists of a 
displacement i ent in the sur- 

rounding dielectric. T i r | >ar1 of this 

current is due to an ether displacement, 
but part is caused by a displacemenl oi 
the ions, which are elastically attached to 
the gas molecules. The 'rain or displace- 

of the io ch molecule i gn 

when the voltage stress is at a maximum, 

hen being at rest and the cm-rent 

zero. [f the voltage is alternating, at the 

ni the voltag ro, the 

ions in the molecule are in midswing and 

at their highest velocity; and '.he dis- 
placement current is then maximum Thus 
t he elastically controlled displacement current 
in the air constitutes a small pari of tl 
parity currenl between the electrodes and is in 



quadrature with the voltage. This is, of 
course, also true of the ether displacement 
current. As practically no friction enters 
into the motion which beats rhythmically 
with the voltage, no energy loss occurs in 
the dielectric, the energy being alternately 
potentially stored in the dielectric and 
kinetically released in the moving ions. 
Corona Current 

If now the voltage is further increased, the 
electric stress at a certain critical point be- 
comes sufficiently great to tear off some of t he 
ions attached to the gas molecules. This 
disruption occurs first, in a layer of air a 
short distance from the surface of the elec- 
trode or conductor, since although the elec- 
tric stress is greatest at the surface of the 
conductor, it has been found that the die- 
lectric strength of the air immediately 
surrounding the conductor is considerably 
higher than that further off. For small 
conductors, the breakdown point is approxi- 
mately .1)7 inches distant from the surface. 
Here the ions are first released and are then 
free to move under the force of the electric 
field in the same way as an electrically 
charged pith ball moves in an electrostatic 
field. At the moment of release, the inertia 
of these ions is small ami, therefore, 1 hen- 
speed is rapidly accelerated until they are 
stopped by collision with other gas molecules 
or ions. If, at the moment of collision, the 
kinetic energy of the ion is above a certain 
value, it may shake off other ions, and in 
this manner the whole space between the 
electrodes becomes filled with electrified 
particles or ions, the positive on the average, 
all moving in one direction, and the negative 
in tin- opposite direction. ( If these collisions. 
some may cause ionic recombinations and a 
neutralization of the electric charge, the 
number of recombinations increasing if the 
gas pressure is raised. Hence, a transfer of 
electricity occurs from one conductor to 
another, the carriers being the ions torn off 

the molecules, either by the electric stress or 

li\ collision, the current at any point being 
proportional to the number of ions passing 
per second. At every collision molecular 
vibration is started and part of the electric 
energy is transformed into heat. If the 
■c is still further increased, a larger 
number of ions are released which attain a 
greater velocity between molecules and cause 
more heat waste and current. It follows. 
thai this current is independent of frequency, 
and has. therefore, the same value at a given 



LONG DISTANCE TRANSMISSION LINE PROBLEMS 



voltage, whether the voltage alternates or is 
held constant. 

Directly the voltage falls below the critical 
value for ionization, all action ceases, only 
to begin again when the voltage rises to its 
proper value in the opposite direction. This 
is practically true, except that a minute time 
lag exists, which is short compared to the 
period of commercial frequencies. It will 
be readily seen from the above that the 
current is a true convection current and is 
in phase with the voltage. It is, therefore, 
at right angles to the capacity current. 

If the pressure of the gas be diminished, 
the number of gas molecules between the 
conductors is proportionally decreased, and 
therefore the distance between the gas 
molecules is correspondingly increased. Under 
such circumstances, the ions have, on the 
average, a longer path to travel before 
collisions occur and, therefore, their speed 
and kinetic energy are greater at collision. 
Hence, each collision is more likely to tear 
off other ions from the molecules, and as 
the number of recombinations producing 
neutral ions is diminished, the current is 
increased. If the gas pressure be further de- 
creased, the ionization current, for a given 
voltage stress, increases until a1 a certain 
critical pressure where the number of mole- 
cules per unit volume has been very much 
reduced, the current becomes maximum, 
that is. the space is saturated with ions and 
on a further decrease of pressure, the current 
falls. 

Under the conditions which exist in high 
voltage transmission lines, it is found that a 
decrease of pressure near the atmospheric 
pressure causes a distinct increase of corona 
i" . and when pressures as low as 20 in. 
are encountered, the loss is considerable. As 
the height of many transmission lines exceeds 
8,000 ft., the highest point reached by the 
Central Colorado Power Li nc being 13,700 ft., 
it is abundantly evident th; relation of 

pressure to corona loss is of i he Brs1 importance. 

Since the critical voltage for No. 1' wire 
is in the neighborhood of 90,000 volt i effective 
or 12li,(]()ll volts maximum, only a small pari 
of the cycle is effective in producing corona 
current at ordinary transmission voltag 
If very much higher voltages were emplo ed, 
not only would the corona current be enor- 
mously increased (so long as the satura 

point is not reached between the conductor I, 
but also the loss would last during the greater 
part of the period. If the no load currenl 



oscillograph record is taken, a kick in the 
curve at maximum voltage is \er\ apparent 
at high voltages when corona is present and 
the shape of the current wave is considerably 

altered. 

When ionization takes place, a brush dis- 
charge can he observed near the uirfaecof the 
wire, where the greatest number of ions per 
unit volume occur and the current density is 
at a maximum. The resistance, therefore, ol 
the air layers surrounding the ivireis consider 
ably decreased, and the effective conductor 
diameter can, therefore, be regarded as greater 
than that bounded by its metallic surface. 
This increase in conductor diameter increa e 
the capacity between the conductors and, 
therefore, the capacity current. Thus, if 
the loss at no load be measured on a trans- 
mission line subject to a large corona loss, Un- 
capacity loss cannot well be calculated from 
formula; and oscillograph records should be 
taken if the corona and capacity loss require 
separating. The high inductive capacity of 
insulator material increases the voltage stress 
near the wires where they are fastened to 
the insulators, and hence the corona loss is 
increased at these points as well as the 
capacity loss. 

Mr. H. J. Ryan considers these matters 
in his paper before the American Institute 
of Electrical Engineers, February ii< > , L904, 
and a considerable amount of work has been 
done by Messrs. C. F. Scott, R. I). Mershon 
and others, especially in connection with the 
effecl of tin- barometric pressure on corona 
loss. Manx- more experiments are. however, 
needed, before the phenomena can be con 

ddered as subjeel to calculation. The varia- 
tion of corona loss with voltage, size of wire, 
spacing between conduct or ., atmospheric 
pressure, state of atmopshere and wire 
urface, and many other conditions must be 
determined before equations can be formed 
to give reliable results. 
Capacity Loss 

The extra currenl carried by the conductor 
due to corona is exceedingly small .and can 
be neglected; in consequence, bhe /"> lo 
the conductor is negligible. The loss all 
in the dielectric between the c< mducl - 
ors. Thus, for constant voltage along the 
line, which will obtain at no load in lines up 
to 200 mile . long at 25 q cle . the corona 
li i . per mile is consl anl al< »ng the lin 
being, independent of frequency. Th 
pacif y current lo . on th othei hand, all 
occur; in the conductor, the currenl varying 



226 



GENERAL ELECTRIC REVIEW 



directly as the voltage and frequency. In this 
case, practically no loss takes place in the 
dielectric between the wh- 
in lines, up to about 200 miles long at 25 
cycles, and in slightly shorter lines at 60 
cycles, the capacity current along the line 
follows practically a straight line law. being 
a maximum at the generator end and zero 
at the receiving end. Hence, if r is the 
resistance per mile of wire, / the capacity 
current per wire at the generator end. and 
/ is the length of line, tlu- current per mile 

i=— = constant . and the loss for a line / miles 
in length is :: | >r!-dl = i-rP. The total 



the current at the generating end, and pre- 
vents it decreasing as fast as it does near the 
receiving end. The total loss, however, 
with a given voltage at the receiving end, 
does not vary as rapidly as the cube of the 
distance of the line length, since the drop in 
voltage at the generator end reduces the 
capacity current correspondingly, which more 
than compensates for the slower drop of 
current along the line. See Fig. 7. 

Calculation of Dielectric Conductance Constant 

The curves. Fig. 8, showing corona and 
capacitv loss, have been obtained by substitu- 
ting a value for g in the transmission line 
equations. This value was derived from the 
observed loss along a 50 mile line operating 











































































































1 












































i (fnitv P/>wr factor at Roth Enas 


























180 








— 












hua/ ''Current 'a <t 'doth Endstfn, >/y Power Factor ffecewnqf^ 




































































160 




































































































































140 












&0A 


'nnzp/)* 
































































— \~r~22i. 


j5«fc# 


'flotyert-. 
































t?fi 






























■ — ■ 


t*2 


"{ortteeei 


y ma End 




















^ 100 












•-& 


Wp r*~. 






























































_^J> 


fc* 


v o//„,/ , 






































k 






















H^T^*5 


^GO/sir C 






























fr so 






















~s^. 


-<&> .' 


rf^* 


"'/?*>>- 






















fi SL 


























5js 


Zf* 


?r,J 


1" 


"^rSj 






















§L an 


































i^i 


---.- 


l 


























gs ou 






































^rt 


























40 




































































































































?o 




































































































































n 



































































50 100 

Generator End 



150 



200 
Miles 



Z50 



JO0 



750 400 

Receiving End 



Fig. 7. 



Capacity Current at 60 Cycles along Three-Phase Line 400 Miles in Length. Using Three No. 0000 Wires Spaced 
10 ft. Apart, 104.000 Volts between Wires at Receiving End. 



loss is therefore .1/' where .l=/'-Y, which is 
a constant at a given frequency, for a definite 
si/.e of wire ami given line Hence, 

the capacity loss for a given transmission 
line varies as the cube of its length up to 
ili«- limits of length just given. Above this 
length, the voltage rises from the generator 
end toward the receiving end. and the 
capacity current does not fall off uniformly 
from the generator end but more gradually; 
that is, the curve of capacity current 
the line is concave towards the abscissa 
cnting line length, provided the line 
resistance is not loo high. The reason for 
this is that the increasi of voltage holds up 



under similar conditions and using the same 
if wire and spacing. As, therefore, the 
voltage is nearly constant, the corona loss 
may be regarded as approximating the real 
value provided the capacity current is not 
seriously altered by the corona loss and that 
no appreciable insulator loss exists. Note 
the change in phase at generator and receiv- 
ing ends due to corona indicated on Fig. 9. 

The dielectric conductance coefficient was 
calculated as follows: The total loss of a 
50 mile line at no load was experimentally 
found to be 2-"> kw., of which 'A kw. was 
calculated as capacity loss, and the remainder 
assumed as corona loss. The voltage was 



UNDERGROUND ELECTRICAL DISTRIBUTION 



11(1,0011 volts between wires. Then the loss 

, 22000 

per mile equals — =438 watts per mile. 



UNDERGROUND ELECTRICAL 
DISTRIBUTION 




By \Y. E. II 



\zi:i. i i\i 



40 

Generator £nd 



/60 200 

Mites ffece/y/njg fnd 

Fig. 8. Amperes. Volts and Power Losses 'Capacity and Corona) 

at no Load along 200 Mile Three-phase Line using Three 

No. 1 Wires 8 Ft. Apart. Operating at 25 Cycles, with 

110.000 Volts between Wires at Receiving End 

Then 
1 



since the dielectric conductance is 



where r is the dielectric resistance per mile 

r- 

: i i ween wires, and since — = the loss per mile, 







438 


r 
= .036X10 _8 = g. 




— , r 


1 10.000 




1 






































-k 




1 


































\ 


Capoc/fy Ofl/y 






































-1 






























— 








*>L. 






























oa 


— »— 


/ Copac/Cyavo' Corona 














'PC 








/ 






— i — 


r 




V ' 






















'■ 


^.03 




-%. 






















tt 




\ 








^"~- 


ht* 


;■ 


2^j 


















L 


V 


\j* 






1 






_£W,. 


,', 


o»-J-_J 




\ 








-a 








1 - 








"a Loss 








<.o, 










-»... 


~Ar~ 










































•^SLf'c 






































1 1 


T-^r^S 


s G0fy 










c 
< 


fcH 


en 


v.- 


4i 

-£r 


1 
a 






St 


i 


feu 


12 


. 






/6 





fl 


>C( 


20 


•-•■ 


~M> 



Fig. 



9. Power Factors Due to Corona and Capacity 
Losses along 200 Mile Line at 25 Cycles 



Corona effect is less masked by capacity 
loss at 25 cycles than at 60 cycles, and the 
example was, therefore, chosen at the lower 
frequency. The constant m in the trans- 
mission line equations, where g is included is 

V (r> + ?m (f + p'C) [cos^ +j sin^] 



where Ian 'fl = 



p(Lg vCr) 
rg-p*LC 



1 



From these values m, and - can be readily 
calculated. 



Sl I'l'l N DEPT., Gl Nl R M El.ECl RII I UMMW 

^ The ungainly aj ce and danger of 

**\ overhead electrical wires have in a large 

8(. measure been accountable for i lie adoption 

§ of the underground system of distribution 
^fc While the first cost of an underground 

| system exceeds that of an overhead, security 
of operation tends to counter-balance this 
difference, for underground conductors are 
entirely free from the effects of storms and 
weather conditions. 

One of the earliest attempts at placing 
wires underground was over fifty years ago 
when Professor Morse of Boston undertook 
in install a telegraph line between Washington 
and Baltimore. His method of laying was 
by means of a large plow drawn by sixteen 
yoke of oxen, the cable being placed on a reel 
secured to the plow and played out in the 
furrow as the plow advanced. It is well 
known that this attempt proved unsuccessful. 
Several years after, the si. -called "pump 
log" was brought into use. This consisted 
of eight-foot lengths with a 3-inch bore, the 
ends butting together with socket joints and 
laid directly in the trench. bogs were 
sometimes of plain wood and, again, treated 
with tar or creosote as a preservative. 

The cement-lined iron pipe was .also used 
to a considerable extent, but this type of 
conduit proved unsatisfactory, one disad- 
vantage being that the pipe was affected by 

: and that the inside euatin 

cemenl sometimes caused corrosion. Both 
types proved inadequate to the requirements 

of ;m underground Ci induit . 

The theoretical conduit should be one thai 
in itself possesses high insulating properties: 
one upon which the .action of water, gas and 
al elements have no effeel and one 
which is permanent and practically indes- 
tructible. These requirements arc found in 
the vitrified clay conduit, which is 
adapted to the purpose and in addition is 
comparatively low in first cosl and in exp 
oi in tailing. 

Another type of conduit , which is at pn 

u ed to tome i xti tit, is I he fibre conduit . It 

is made from wood fibre treated with an a iphalt 

compound which the makers claim renders 

kaline proof . Thestandard 



22S 



GENERAL ELECTRIC REVIEW 



length is about five feet . with a 3 in. bore and 
is smooth inside; therefore, cables are safe 
from injury when being drawn in. This type 
of conduit is usually laid in concrete and 
lengths are joined by a butt joint which 
keeps them in alignment. 

To return to the vitrified clay conduit, this 
is without doubt the most popular type in use. 
Duct sections are supplied with one, two, 
three, four, six, nine and twelve holes, the 
standard single duct being 18 in. in length 
and 3 in. internal diameter. Sections of more 
than six ducts are difficult to handle and are 
not made to a great extent on account of the 
liability to warp during manufacture. 

The flexibility of this system allows ob- 
structions such as gas, water and sewer pipes, 
to be overcome by laying the duct line over 
or under them, and in some cases to split the 
duct line, placing part above and part under- 
neath. In any case, ducts should be laid with 
such a gradual grade as to permit cables to be 
pulled in without injury to the lead sheath. 
Also, the use of short lengths permits the 
laying of curves of long radius, oftentimes 
doing away with additional manholes. The 
duct is generally laid on a bed of concrete, 
usually :! in. thick, surrounded by walls and 
red with concrete of the same thickness. 

In laving single duct, a mandrel about 
:{(i in. long, slightly smaller than the internal 
diameter of the hole and having a rubber 
gasket on the end slightly larger than the 
diameter of the hole, is drawn through the 
dud as it is being laid. This removi 
loosi rticles of cement and stones and 

makes sure that there are no obstructions to 
injure the cables; further, care should be taken 
to insure that duets are perfectly aligned. 

In laying a section of conduit the engineer 
in charge should lay oul his grades so that 
all the duets in e: on drain into one 

manhole, or else break the grade so as to 
drain into two adjacent manholes, thus 
preventing injury to the cables after they are 
installed, from the freezing of water which 
may find its way into the duet line and settle 
in any pocket there may be. 

For long straight runs, when there arc no 
obstructions, the multiple forms of duct are 
usually used. These arc laid in practically 
the same manner as th ducts, except 

thai joints are aligned by the use of dowel 
pins. 

One objection to multiple dial is, that 
between any two duet sections there is only 
one wall and it is impossible to break joints 



as with single duct; therefore, there is a 
possibility of a burnout in one duct finding 
its way to a neighboring one. 

With single conduit, where there are two 
thicknesses of wall between any two ducts 
and where joints can be staggered, this 
danger is practically eliminated. Single 
duct, however, requires experienced labor in 
installing, while multiple duct may be laid 
by ordinary laborers. 

Manholes are necessary in order to facili- 
tate the drawing in or out of cables in the 
system and are generally located at street 
intersections or at sharp bends in the duct 
line. The maximum distance between hi 
should not exceed 500 feet, for at greater 
distances the cable is liable to break or 
stretch from the excessive strain during the 
process of pulling. 

The general manhole c< mstrucl ion is of brick, 
although the present tendency is towards 
concrete holes whenever possible, as the aver- 
age cost of concrete manholes is approxi- 
mately two-thirds that of first class brick. 
Concrete holes are usually made from wooden 
forms of take-down design which may lie u 
indefinitely. Bottoms of manholes are usually 
of concrete, with a hollow in the center which 
allows water in gather. When possible, 
connection with the sewer through a I 
should be provided to remove any sun. 
Water which may work in around the cover. 

Referring to manhole covers, authorities 
do not agree as io whether a single or double 
cover should be used. The single cover 
simply fits in a cast iron frame at street level. 
Inside of this there is sometimes another 
cover resting on a rubber gasket, bolted and 
secured mi as to prevent water entering. The 
main disadvantage of this inner cover is that. 
in case sewer gas or illuminating gas escaping 
fnnn leaky mains finds its way into the hole. 
there is no way of escape and this accounts 
for the majority of manhole explosions which 
occur. 

It is believed by many authorities thai the 
single cover is preferable and this should be 
supplied with several air holes to allow gas 
to escape. Theoretically these vent holes 
should be conical in shape with the small 
opening on top to prevent them from becom- 
ing clogged. It is true that surface water 
finds its way through these vents into the 
hole, but this is taken care of by the sewer 
connection. It is well known that, with a 
large number of cables carrying heavy loads, 
considerable heat is generated and a large 



UNDERGROUND ELECTRICAL SYSTEMS 



229 



percentage of this is dissipated through the sur- 
rounding earth, but by using perforated man- 
hole covers, it maybe got rid of more easily. 

In order to support the cables which must 
necessarily pass through the manhole ii is 
customary to provide some sort of a device 
on which they may rest. In brick holes, 
brick shelves are built into the sides a1 
suitable distances apart upon which cables 
are placed. Also with concrete manholes the 
wooden forms may be so designed as to pro- 
vide for concrete shelves. The use of shelves 
for cable-supports is especially desirable, for in 
case of trouble occurring on one cable, the 
neighboring cables are protected to a certain 
extent from injury. Oftentimes with brick or 
concrete manholes, iron cable racks, provided 
with arms adjustable at will, are built in. 

A conduit line composed of a large number 
of ducts is undesirable, one reason for this 
being that it is almost impossible to support a 
large number of cables in one manhole. I' is 
advisable, therefore, to divide the under- 
ground lines from the generating station, in- 
stalling a portion through two or more streets, 
if possible; but if the station is so situated : ha1 
the entire output must pass through one 
street, a single conduit line with twin man- 
holes may be used. 

With a single duct line entering the station 
it is rather difficult to dispose of the cables 
satisfactorily. 

Coming to the question of cable, the size 
of duct determines in a way the size of cable 
to be used. Eor the standard 3 in. dud for 
working pressures of 1500 volts or less, the 
largest single conductor that should be in- 
stalled is a 2,500,000 cir. mil., or a concentric 
1,000,000 cir. mil. cable, while the large I 
three-conductor cable is one of 100,000 
cir. mils. From 1500 to 3000 volts, the 
largest single conductor should be a 2,000,000 
cir. mil. en Lie or a concern ric cable of 750,000 
cir. mils.; and the large.-- three-conductor 
cable, one of 100,000 cir. mils. For 6000 
volts (usually three-phase delta connected), 
the largest three-conductor cable is oni 
250,000 cir. mils.; for L3,000volts,3 conductor 
1 i); and lor 20,000 volt 5, :: conductor 1 0. 

As the cost of the duct line is independent 

: i] co dvisable tocl i uch 

cable as will reasonably fill the duet area, 
thi reby (titling down the conduit investn* nl 
to a minimum lor the amount of energy 
transmitted. In laying out ;m mderground 
system, it is advisable to provide extra duets 
to take care of future requiremei 



For underground work, three types of 
insulation are used; viz., paper, varnished 
cambric and rubber; paper being the cheape ;1 . 
varnished cambric intermediate and rubber 
the most expensive. For dry ducts, where 
there is no danger from corrosion of the lead 
sheath or where electrolysis is absenl or may 
be guarded against , paper cables may be u ed 
Paper is also used to a great extent for trunk- 
lines. Paper cable musl no1 beusedwitho 
lead sheath, lor the life of a paper cable is 
dependent upon the sheath, the presence oi 
moisture causing the insulation to break down 
almost immediately. Electrolysis, therefore, 
proves disastrous to paper cables. 

Varnished cambric cables have all the 
good qualities of paper cables ami may be 
used in almost any place where rubber cables 
could be used. These cables arc built up of 
successive layers of lapped, varnished cambric 
tape, with plastic compound between layers, 
this compound permitting the layers to slide 
on themselves when the cable is bent, without 
reducing the thickness of insulation between 
conductor and lead. This type of insulation 
is waterproof, ami the ends of the cable do 
not necessarily have to be sealed to prevent 
moisture entering, as with papier cable. This 
is also true of rubber insulated cable. Since 
varnished cambric tape is used in insulating, 
the copper core must be in the center of the 
cable, while with rubber insulation for heavy 
copper cores, used for horizontal runs at high 
temperature, there is a tendency for the rubber 
to soften, thus allowing the core to drop and 
reduce the thickness of insulation between 
e, i] i] ier ci .re and lead sheath. 

Varnished cambric cables with a braided 

finish may be used for inside work, as the 

insulation does not absorb moisture. These 

cables, unlike paper insulated one-., are not 

-ii -h affected by electrolysis. 

Rubber insulated cables are used where 
i is constant moisture and almost in- 
variably for submarine use. 

Paper cables ma] be benl to a radius equal 
to eight times the outside diameter of the 
cable, while rubber and varnished cambric 
may be bent t<> a radius of six times this 

[ue. 

For direct current ],,■. - ilway 

feeders, single conductor cables are generally 
used [n some cai i wh inial] 

feeders run parallel for any con iderable 
i e, n is frequently desirab mbine 

them into one tble running to thi 

lion. 



230 



GENERAL ELECTRIC REVIEW 



For the grounded side of street railway 
feeders, or the neutral of three-wire Edison 
systems, a bare wire may be used, but this 
should not be run in the same duct with leaded 
cables. An ordinary weatherproof finished 
wire is often substituted for this bare wire. 

Low tension feeder cables are frequently of 
the two-conductor concentric type with pres- 
sure wires in the outer conductor. The carry- 
ing capacity is slightly less than that of a two- 
conductor cable leaded flat as there is less 
chance of radiation; but the concentric type is 
easier to install and is much more economic of 
duct space. 

For alternating current single-phase two- 
wire systems, the duplex type is preferable 
unless many taps are called for, and if so, 
single conductors are sometimes used on 
account of the greater ease in making joints. 

The largest solid conductor recommended 
is 4; larger conductors are too stiff to handle 
and should he made stranded. 

Duplex or figure 8 cables larger than 250,000 
cir. mils, are liable to kink in handling and 
are not used to any great extent. For larger 
cables the I wo conductors may lie stranded up 
with fillers to make them round, and the lead 
lied. Any size of duplex (Fig. 8) cable must 
have special care in installing to prevent 
kinking. 

For three-phase work, it is advisable to use 
three-conductor cables; for, with this con- 
struction, then' is no loss theoretically in 
the lead sheath, and, if necessary, telephone 
cable may be run in the same duet system 
without disturbance. 

On low tension systems, single conductors 
are frequently used on account of the ease 
in making service taps. 

The chief advantages in using three- 
conductor table are: cost of installing is less 
and installation is easier, while the first cost of 
a three-conductor is approximately the same 
as that of three single conductor cables. 

Three-phase cables are more economical of 

duet space than either ingle or two-con- 
ductor cables. Three-phase Y connected 
cables an- generally run with grounded 
neutral and the thickness of insulation be- 
tween conductor and ground need only be 
seven-tenths the insulation between con- 
ductors, thereby allowing a slightly lar 
cable to l.c installed in conduit than a three- 
phase delta ed, where insulation be- 

een conductors and between condu 
and ground is the same. 

The general practice in three-phase cable 



work is to use the so-called split type of 
insulation, placing half of the total thickness 
required on each conductor, stranding the 
three conductors up with jute fillers to make 
round, wrapping the three conductors with 
the second half of insulation, and applying 
the lead finish. This makes a more compact 
cable than when applying all the insulation on 
each conductor and is somewhat cheaper. 

For are circuits, single-conductor and also 
duplex cables are in general use. Where 
several circuits run parallel for any distance, 
they are sometimes combined into a multiple- 
conductor cable, for if several single conduct- 
ors are run in one duct the lead sheath is 
liable to be injured in installing, and if one 
cable burns out, it is likely to injure one or 
more conductors. 

( )ne danger in underground cables which 
should be guarded against is electrolysis, 
for no manufacturer will guarantee his 
product against electrolytic action. The 
amount of electrolysis depends primarily on 
how near the cables are to electric railway 
lines, the distance they run parallel, and the 
condition of the return circuit of the railway, 
also the proximity of water pipes and gas 
mains. Electrolytic action occurs at the point 
where current leaves the lead sheath; there- 
fore, with leaded cables, it is customary 
where this danger exists to provide suitable 
grounds at intervals along the system. 

Sometimes this is accomplished by driving 
an iron pipe into the earth at each manho 
This can be tested out with an electric 
current of about lid volts, connecting one 
side of circuit to pipe and other side to an 
adjacent hydrant, ami then driving in pipe 
until sufficient current passes to make sure 
that a good ground is obtained. It may be 
necessary to drive as much as thirty feet of 
pipe or more in dry soil before a good ground 
is reached. It is sometimes customary to 
provide grounds by burying large copper 
plates in the earth, embedded in coke In any 
case all lead sheaths in the manhole should 
then be connected to ground. 

With railway systems, the negative side of 
the generator is usually grounded and the 
lead sheath of the return circuit should be 
connected to 'he negative side of generator 
by suitable copper cable. If precautions 
taken, the danger from electrolysis may be 
reduced to a minimum. 

After the duct lint' is installed it is good 
practice to pass a mandrel through each 
duet, thus removing all obstacles and making 



UNDERGROUND ELECTRICAL SYSTEMS 



231 



sure that ducts align. This is sometimes ac- 
complished with rods about three feet long, 
provided with a coupling device, and as main- 
rods as are required to reach from one manhi tie 
to another are successively joined. 

At the same time that the mandrel is pulled 
through, an iron "fish" wire is also drawn in 
and left until it is desired to install cables 
in that particular duct, when the fish wire 
serves to pull through the heavy rope which 
is fastened to cable by a cable grip. 

There are several methods of pulling cable. 
Short runs of light cable are sometimes pulled 
in by hand, but for heavy cable it is necessary 
tn use some form of winch or manhole cap- 
stan. Both electric and gasoline-driven 
winches are being used with success. 

It is advantageous in drawing in cable to 
have a man in the manhole where he can 
watch cable and make sure that it is not 
being pulled in faster than it is unreeled, thus 
preventing sharp bends which might prove 
injurious. He can also smear the sheath 
with a cheap grade of vaseline, which in the 
case of heavy cables makes them slide 
easier. 

All cables to be installed in one duct 
should be drawn in at the same time, for if a 
cable is pulled in afterwards, it is almost sure 
to injure the lead of cables already installed. 
It is also poor practice to draw out one cable 
from among one or more others. 

Enough slack should be allowed to permit 
cables being passed around the sides of 
manhole, and also to permit jointing, for 
occasionally cable ends are injured during the 
process of drawing in, necessitating cutting 
back far enough to remove injured por- 
tion. 

With single conductor cables, where a butt 
joint is used, the ends in the manhole should 
rlap slightly, and for multiple conductor 
cables, where joints are staggered, the overlap 
should be enough to take care of this. 

Ends of duct should be provided with lead 
collars on which the cable re its, thus prevent- 
ing sharp corners of duct from injuring the 
lead -heaths. It is also good practice lo 11 ,e 
rubber bushings made of old hose between 
iron hangers and cable, which prevenl lea!. 
of stray current from one cable to another. 

('allies in manholes an- often protected by 

iestos listing or by enclosing them in 
split duct, thus preventing the danger of a 
burnout on one cable from affc< ing another. 
This also protects cables against injury from 
careless workmen and prevents their being 



used for steps in descending into a manhole. 
All sharp bends should be avoided. 

With high voltage leaded cables of 2500 
volts and over, there isati ndency to puncture 
the insulation at the ends of lead sheath; 
therefore end bells are required at the station 
end of system, and also at the farther end 
where cables change from the leaded under- 
ground type to the braided overhead. The 
are generally of spun brass wiped to the lead 
sheath, their object being to flare out the 
lead, thus preventing a breakdown at the 
ends. 

With paper insulated cables, the bells are 
made long so as to allow of the joint being 
made inside the bell. A cap is provided, 
through which the overhead cable end passes, 
and after the joint is completed, the bell is 
filled with a compound which prevents 
moisture entering and also acts as an in- 
sulator. 

Underground systems when connected to 
overhead should be protected from lightning 
discharges by suitable arresters placed on 
second or third pole from the end of the 
cable. 

It is desirable, after cables arc installed and 
connected, to test them for five minutes with 
about twice the working pressure to make 
sure thai there are no weak points due to 
imperfect jointing, or injury during installa- 
tion. 

Junction boxes arc a necessity on low 
voltage systems and are installed in manholes 
at feeding points Or street intersections so 
that in ease of local trouble the feeders and 
mains may be disconnected. 

Services are usually run from manhole or 
from service boxes located between man- 
holes at street surface. Iron pipe is frequently 
used, ;o laid as to drain into manhole. For 
long service . cable with band iron armor 
finish is laid directly in the earth. The band 
iron protects the cable from injury, but it is 
customary to place a heavy plank over the 
cable so that in future excavations workmen 
will not injure the cable with a pick. 

Service cables are sometimes connected to 
mains through service boxes placed in man- 
holes. This arrangement is inconvenient 
in case of trouble; therefore il is customary 

to place service boxes on customers' premises. 
There are several installation o .died 

Edison tube systems still in use, bul at 
pre cut the popular drawing in system which 
this article deals with is used almost exclusive- 
ly throughoul I hi o mntry. 



2;j2 



GENERAL ELECTRIC REVIEW 



MOTIVE EQUIPMENT FOR ELECTRIC AUTOMOBILES 

By H. S. Baldwin 



Since the introduction of the electric auto- 
mobile manufacturers of electrical apparatus 
have been active in the development of auto- 
mobile equipments, consisting of motors. 
controllers and resistances designed to give 
the most efficient and economical service and 
in conserve the battery. 

In the earlier automobiles, designers gener- 
ally employed two low-speed motors, each of 
which operated the driving wheels by means 
of single reduction spur gears. Of late years, 
however, this practice has been largely aban- 



with the single reduction gear drive of the past. 

It was realized by the General Electric 
Company that the high-speed single motor 
drive represented the simplest," most prac- 
tical and efficient form of equipment that 
could be offered, and as a result they pro- 
ceeded with the development of the so-called 
GE- 1 020 line of motors, of uniform mechanical 
construction throughout. 

In addition to motive equipment, this Com- 
pany supplies specially designed; [charging 
equipments, comprising rectifiers, motor gener- 



*^t ] jvgfc-^^ 



%-^aii^He 



C ' 

H - 


>- -o o- -o 

3 O O O- >-, 

>--o | o--o 
) o-f-o o->* 
)--o 1 — o 
> O-j-O O- 1 



°e a r .- 




• - r -V - 



- 



Fig. 1. Diagram of Connections of Electric Automobile Equipment 



donedinfavorof the singl< motor and counter- 
shaft with double reduction i hair • ransmission. 
The advantage claimed for tin- single motor 
drive may be briefly summed up as follows: 

1. It affords a material saving in weight. 
cost and pace occupied a againsl two 

oi practically t he same capacity. 

2. By the Use of double '.duel il Ml 

ing with countershaft, it is possible to 
design the motor for higher speed, which 
' and insure electrical 
efficiency, 

3. It further permits the motor to be 
mounted on the chassis, well up from the 
ground, which arrangement was not possible 



ator sets, switch boards, rheostats complete 
with controlling panels, and many other 
useful and desirable appliances. 

In order lo me. i the requirements of auto- 
mobile manufacturers, the motors have been 
made in six different sizes, each of which can 
lie supplied in several electrical ratings. It will 
readilj beseenthat this line is the most complete 
i \ it offered, and that a motor can be selected 
for any vehicle, from the smallest runaboul 
to the heavy 5-ton truck. 

The motors are of unique mechanical de- 
sign Fig. 2 . the frame and one head being 
from a single piece cylindrical steel 
casting, machined from end to end. By this 



MOTIVE EQUIPMENT FOR ELECTRIC AUTOMOBILES 



233 



construction the minimum of weight and 
maximum of strength are combined. This 
feature is original with these motors and is 
not tn be found in those of other make. 

It is of paramount importance to protect 
the storage battery, and all of the motors 
under consideration are de- 
signed with this object in view. 
They have a steep torque curve 
and give about five times the 
torque for two-and-a-half times 
the current, throughout the 
limits of their capacity. It 
might be well to add a wi >rd of ex- 
planation as to this statement. 
To obtain long life and efficient 
operation, the storage battery 
should not be discharged more 
rapidly thanattheone hour rate. - Runabout TyP e; w 
To start and accelerate an elec- 
tric automobile requires approx- 
imately five times the running torque. Again, 
the average maximum grade encountered in 
cities is about 7.(i per cent., to climb which 
also requires about five times normal torque. 
It will, therefore, readily be seen thai a prop- 
erly designed electric automobile motor, 
having the above characteristics, will accel- 
erate tlie \ e i riclc and climb any ordinary grade 
without exceeding the one hour disi harge rate 
of the battery. 

The standard motors have cast iron heads 
fitted with the most improved annular ball 
bearings, which somewhat increase the effi- 
ciency, reduce the overall Length of the fra 
and require only occasional lubrication. All 
electrical factors are liberal, permitting these 
motors to lie run at high overloads for co 
siderable periods of time without injury. The 
commutators are composed of a large number 
of bars, and observations covering several 

rs 1 use of motors in service ind hat 

the commutation is practically perfect, greal 

e having been taken to secure thi result. 
Special graphite brushes ol large ana are 



used and the current pe inch of 

brush contact is lower than usually obtains 
in electric mot. n- | irad ice. 

Two motors, namely the GE-1022 ami 
GE-1027, have only recently been added to 
the line, the former being suitable for 3-ton 




eight 150 Lb. 5-Ton Truck Type; Weight 660 Lb. 

Fig. 2. General Electric Automobile Motors 

and the latter for 5-ton single motor trucks. 
All motors are of the 4-pole type, and with 
the exception ol the mailer sizes for run 
abouts are designed to operate at 85 volt-. 
experience indicating this voltage :<> be most 
advantageous when the lead battery i 
employed. The runaboul motors are built 
01 iperate at 18 or 60 volts, as desired 
Special a1 bention is called to tin/ fact thai 
all motors arc constructed so that the shaft 
can be removed without disturbing the 
commutator or winding. This feature afford 
a1 flexibility and permits a changi oi bail 
at small expense, to accommodate special 
ci mditions or when worn. 

In the manufacture of the field i 

railway prai tice i i losely followed, especially 
as regards insulation and treatment; tlm 
the coils are adapted to withstand :even 

en ice e litions. Copper is used liberally 

throughout in the complete line of motors. 
This is especially true as regards the field 
coil . a feature which, together with high grade 
brushes, ball bearings, and commutators <4 



STANDARD AUTOMOBILE MOTORS 



Type 


Volts 




R I'M. 

-.'Ill III 

l 21 H i 

121 Ml 

1 _'l II 1 
900 


Vehi 




GE-inux 
GK 1020 
GE-HiL'.-, 
GE-lii.'i; 
GE 1022 
GE-1027 


is 

85 
85 

s;, 
85 
85 


26 

I'll 
22 
28 

i,i. 


Runabouts 

delivery 
1000 He del. 
2000 He del. 
:; ton truck 


i, 

<; 3 

1 2 

1 L' 
4 L 
4 



21 'A 



GENERAL ELECTRIC REVIEW 



small diameter, insures the highest possible 
electrical efficiency, so important when the 
storage battery is the source of power. 

It will readily be seen that the General 
Electric automobile motors are practically 
universal in form, and can be adapted 
to many different methods of sus- 
pension and mounting. By use of the 
accurately machined motor frame, it is 
possible to meet all practical require- 
ments of automobile manufacturers 
as to mounting, since supporting 
brackets or cradle can be attached 
directly to the steel easting by means 




If TJ If IT IT IT IT IT If TT 

Fig. 3. New Controller for Automobile Motor 

of screws. This results in quicker deliveries 
and lower costs, for the reason that a large 
amount of engineering and developmental 
expi ti >e is eliminated. 

ood controller is scarcely less important 
than a good motor, and it is essential that 
each be selected with reference to the other 
and the nature of the service to which the 
automobile is to be put. All General Electric 
automobile ci mtrollers embody the conl inuous 
torque principle, which insures freedom from 
jolts Aiu- to opening of circuit when passing 
from series to multiple connection of field 
eoils. This is an important feature, which 
adds much to the plea ure 
cars and to the life of large trucks. With the 
single motor equipment, series parallel ar- 

menl of fields is the standard form of 
control, resistance being used on intermediate 
In the i a e oi contn pliers E> >r pleasure 
vehicles, it is customary to have a com- 
paratively large number of points, to permit 
of slow operation in cities where the traffic is 
congested, and higher speed over park and 
country roads. I rcial trucks as a 

rule do not require this fine gradation of 
speed and, therefore, have only sufficient 



notches to safe-guard the chain or gearing of 
the transmission. 

A new controller has recently been designed 
I Fig. 3 i , which contains all the good points of 
the several types heretofore offered, with the 
additional advantage that many of the same 
parts can be used for different systems of 
connection, thereby insuring uniformity of 
construction. The new controller is of the 
cylindrical drum type and is operated by a 
pinion and sector at one end. The sector is 
mounted on a countershaft which carries 
the operating hand lever. Drum contacts 
are made from drawn copper tubing, screwed 
in place on a treated wood drum, and horn 
fibre spacers are inserted to insure smoothness 
of operation and to prevent sparking. Con- 
tact fingers are of rolled copper stocl 
cured to phosphor bronze springs. The 
controller is designed throughout with a view 
to withstanding rough usaj 

An operating handle of new design has been 
provided, made from drop-forged steel and 
having the advantage that it can be formed 
to suit the automobile manufacturer. This 
is very desirable, since there is a great 
diversity of opinion as to shape of seat and 
body outline. 

To make the equipment complete, a light 
cast iron grid resistance is employed Fig. I , 
This again is of sturdy construction and 
heavily insulated with mica. All terminals 
are drop-forged. 

An important point in connection with 
these motive equipments is that the term- 
inals, leads and contacts of each component 




Fig. 4. Cast Iron Grid Rheostat 



part are marked with letters in accordance 
with the wiring diagram, so that the n 
sary connections in an electric automobile 
can be made by those not having special 
electrical knowledge. 






235 



APPARENT CHANGE OF RATIO OF TRANSFORMATION 

IN THREE-PHASE TRANSFORMERS 

By G. Paccioi i 



Sometime ago three single-phase trans- 
formers were installed to operate a rotary 
converter. The primaries of the three trans- 
formers were connected " Y ", and the econd- 
aries "V" diametrical. The difference of 
potential between primary lines was 11,000 
volts, and the normal voltage of each second- 
ary winding 2 in volts. 

The three transformers were connected to 
the high tension feeders (11,0(10 volts) and 
the- voltage across each secondary winding 
was measured at no load. This voltage 
resulted to be 235 volts instead of 210. 

The leg voltage corresponding to 1 l,i)()0 
volts "V" is 6360 volts and the ratio of the 
transformer windings was exactly 6360:210; 
therefore there was no apparent reason 
for the higher secondary voltage. An 
investigation of the trouble immediately 
disclosed the fad that the secondary 
voltage was increased at no load from 210 
to 235 volts by a triple frequency com- 
ponent of the voltage. 

A brief review of the phenomena in- 
volved in the case will probably prove 
of some interest. 

It is known that if a single-phase 
transformer is excited by a sinusoidal 
electromotive force, the magnetizing 
current is considerably distorted, owing 
to the characteristics of the iron in the 
core 

Pig. 1 shows the curve of exciting 
current of a 2o kw. transformer at normal 
excitation. The electromotive force 
applied across the exciting winding was a 
perfect sine wave, and its effective value 
460 volts. The analysis of the complex 
wave of current gives the following 
results: If the maximum value of the 
complex wave is assumed to lie 100, the 
fundamental component will have a 
maximum value of .")7.-'i, the third har- 
monic a maximum value of 30.2, the 5th 
harmonic a maximum value of 10.0, and 
the 7th harmonic a maximum value of 
2.96. The predominant overtune of this 
wave is, therefore, the third harmonic, 
and this is generally the ease with 
transformer. 

Now let us take three of tl -se 2.") kw. 
transformers and connect their exciting wind- 
ings in "Y", leaving the secondary windings 



disconnected, then apply across the lines 
70."> volts, which corresponds to a leg vol 
of -100 volts. Each of the three transformers 
requires fur its magnetization a triple fre- 
quency current, and since the electromotive 
force-, aero cadi transformer are 120 

apart , it is e\ ident that the magnel 
izing currents and their high frequency 
components will have the same phase dis- 
placement. The triple harmonics of the 
magnetizing currents will then be di placed 
120 degrees; but 120 degrees constitutes 
exactly one wavelength of the t riple harmonic, 
and therefore the three triple frequency 
components of the magnetizing current in the 
three transformers will be in phase with each 




IQ 40 M 60 100 \?0 140 160 180 OX) 
Decrees 

Fig. 1 

other. Tin- arrows in Fig. 2 represenl tin 
directions of the three triple frequency 
currents in the legs of the "1 l; in- 

stant. It is obi IOU that under the e con- 
ditions such current, cannol flow, and 



236 



GENERAL ELECTRIC REVIEW 



therefore the flux in each core can no longer 
be a sinusoidal flux and the electromotive 
force across each individual transformer 
cannot be a sine wave. In other words, 
although a sinusoidal e.m.f. is applied be- 




Fig. 2 

tween AM. BC, and CA, the electromotive 
force AN, MX and CN must contain 

high frequency components which are 
to restore the equilibrium. 

795 volts were applied acr< i 
of the "Y" system, giving a lej i of 

160 voll . and the electromotive force 
acmss AN, MX and CN was measured 
and resulted to be 525 volts instead ol 
Kin. T mdary windings of the 

wen no1 connected to- 
gether. Fig. 3 gives the curve of this 
electromotive force and its analysis. If 
the maximum value of the complex wave 
is taken as Kill, the maximum values of 
fundamental and the 3rd and 5th 
harmonic are respectively (i 1.5, 33.3 and 
I'.!'. The wavi of the line current was 
taken a1 i he same time and en in 

I. The analysis of this current 
wave gives LOO maximum \, 84.2 

maximum fundamental, 21.8 maximum 
5th, and 3.3 maximum 7th. Thiscurrei 
is then free from third harmonics, as we 
had anti ipated . bul the triple frequency 
distortion, which could no1 appear in 
the wave of cum ars in the wave 

of electromotive > If we neglei 

the 5th harmonic, which is comparatively 

all, and a >sume thai the electromotive 
force across each transformer i com- 
posed of a fundamental and third har- 
monic, we can immediately deduce the 
value of this third harmonic. 

The fundamental i> equal to 460 volts 
i the ii' irma li oltage correspi mding ti i 795 
volts across lines) and the third harmonic is 

•" |Ual1 " v^ 165". 250. 

In fact, it is well known that the effective 
value of the sum of two effective vectors of 



different frequency is equal to the square root 
of the sum of their squares. We see then that 
the " V" connection on the exciting side does 
not allow the flow of any triple frequency 
currents, and that, in consequence, the vol- 
tage across each transformer is composed of 
a fundamental wave of 460 volts plus a 
triple frequency component of 250 volts. 
This latter component is equal in all three 
transformers and affects equally the three 
voltages AN, MX and CX. Furthermore, the 
difference of potential between the point X 
and the neutral of the generating system 
is evidently equal to 250 volts, and has a 
frequency three times the fundamental. 

To remedy this distortion of the voltages, 
two methods can be followed: Firs;, the 
neutral X of the " Y" can be connected to the 
neutral of the generating system: and second. 




Z0 40 60 80 100 IZ0 140 IM 180 ^00 
Decrees 

Fig. 3 

the secondary windings of the three I 
tiers can be delta connected. 
In the first case, the three triple frequency 
currents of each leg will flow in the neutral 

wire and the magnetizing current of each 
transformer will have the same value and 



CHANGE OF RATIO IX THREE-PHASE TRANSFORMERS 



237 



shape of wave as in the ease of single-phase 

connection. If follows thai the electromotive 
force across each transformer will be a sine 
wave and equal to 460 volts. In the second 
case, the triple frequency currents which 
cannot flow in the primary winding circulate 
in the closed secondary delta because the 
direction of these currents is the same in the 
three sides of the triait 

This can easily be seen by remembering 
that the secondary electromotive force o 
transformer must be an exact reproduction of 
its primary electromotive force. Then, if the 
primary electromotive force has a triple 
frequency component, the electromotive force 
induced across each side of the secondary delta 
must also have a triple frequency component. 
These triple frequency electromotive forces 
induced across each side of the delta'assist 
each other, as shown in Fig. 5, and produce 
in the closed delta a triple frequency current 
which is magnetizing in character and excites 



100 



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V 


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fr 


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the triple frequency magnetizing current 
through the resistance and reactance 

of the windings, and thai the volta 
each transformer will be practically a sine 
wave. 
But if ili< i condary delta is open and the 
















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riple frequency flux m jive a 

sine wave of flux in the tran former. The 
final result is that aero,, each ide of the 
delta there will be only a small tripli 

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Fig. 5 

primary neutral not connected to the neutral 

of the generating system, each leg of the "Y" 

has a triple frequency component of the 

electromotive force across its terminals, 

which is also present at the terminals of 

each secondary winding. 

The common method of deducing the 
voltagi across the secondary windings 
of a three-phase system, the primary of 
which is "Y" connected, consists in 
dividing the voltage between prin 
lines by i 3. This gives the vol 
across each leg of the primary, and this 
voltage multiplied by the ratio of turns 

: e eo mdarj \ < iltage. In the ci 
just mentioned, this method of calcu- 
lation is incorrect, because, as we have 
seen, the leg voltage of the primary and 
the voltage across the econdary wind- 
ings arc considerably increased by the 
nee of a triple harmonic. 
This is the reason for the apparent 
discrepancy in the ratio voltages referred 
o i the beginning of this article. In 
that case 1 1,000 volts were impri 
across the primary lines, giving 631 

the corresponding l< , Since, 

however, the neutral wa no1 connected 
to the neutral of the generating system, 
£00 and the econdan windings were open 

diametrical. " Y"), a I riple 
componenl of the voltage was active 
across i he "Y ". This com- 

ponenl was reproduced aero 3 I he ter- 
minal- of the secondary and increased the 
ondary voltage from 210 to 235 volts. The 
value of 'In - compi menl i 

\ 235* — 210 s :i .Its on the secondary 



238 



GENERAL ELECTRIC REVIEW 



side. This means that the triple frequency 
component of the e.m.f. on the primary side 
must be (V >, in 

105 X^" = 3190 volts. 

This is the difference of potential between 
the neutral of the " Y" and the neutral of the 
generating system, and the potential across 
each primary leg is 

\ 6360 2 + 3190 2 = 7100 



X. 



6360 7100 



210 



1':;.". 



that is to say, the ratio of 



voltage measured across primary and second- 
ary windings of each transformer is equal to 
the ratio of the turns; but it is impossible to 
deduce the leg voltage from the voltage across 
lines by dividing it by the coefficient 1.73. 
Conditions of this nature are very frequent 
in three-phase systems. 

If the transformers are loaded, the apparent 
change in the ratio of voltages disappears at 
once. Therefore, the presence of the triple 
frequency e.m.f. in this case has practically 
no effect on the operation of the transformers. 



FURNACE ECONOMY 

By F. W. Caldwell 



Manv power stations are operated uneco- 
nomicallv, due to indifference or ignorance 
in regard to the operation of the boiler plant. 

Although there has been a great deal of 
discussion concerning the value of determining 
the quantity of ('<>•_. (and neglecting other 
gases) in boiler furnaces, the opinion seems 
to be very definite that some form of indica- 
ting apparatus is of great advantage to the 
firemen as well as to the plant operator, but 
that there is no apparatus which can entirely 
replace the trained eye in determining the 
best kind of lire. 

Perfect combustion, high furnace tempera- 
ture, high velocity of gases over heating 
surfaces, ami low stack temperature are all 
advantageous, ami the best efficiency of 
evaporation is attained when all of these are 
a simultaneous maximum. Gas analy- 
sis is influenced by the first two 
conditions, slightly by the third, ool 
at all by the fourth, ami is itself a 
perfect measure of none. 

If there are holes in the lire bed. 
the oxygen content will rise and the 
amount oi carbonic acid will fall in 
proportion. Gas analysis will reveal 

I he |>i I such h( iles, and Si i will 

the eyi coupled with an examination 
of I he tin- bed with the usual fire b >ols. 

If a fire is thin ami is passing too 
much an M analysis will give the 
same indication that is given when 
a lire bed contains holes, and it will 
not determine which of these troubles exists 
The usual draft gauge and fire tool are the 
final instruments and might havi been used 
in the hrsl place. Again, leaks in the setting 
give this same oxygen indication and musl b< 



determined separately, independently of gas 
analysis. 

The most common errors are the admission 
of too much air to the furnace, uneven fires 
and poor methods of tiring. An analysis of 
the flue gases is naturally the best evidence 
of what is taking place in the furnaces. 

The flue gases consist principally of nitro- 
gen (N), carbon dioxide (('(>,'. oxygen (O a ), 
and carbon monoxide (CO), the proportions 
depending upon the amount of air admitted 
to the furnace, the completeness of combus- 
tion and the quality of the coal used. 

Generally speaking, a low percentage, of 
COn indicates the admission of too much air 
to the furnaces and a low boiler efficiency. 
A high percentage ol CO always indicates 
incomplete combustion and a low boiler 



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Curve Showing Percentage of CO; ; n Flue Gases 
for Different Boiler Efficiencies 

efficiency. The correct percentage of 

has always been subject to more or less 
discussion, the estimate varying from I 
II per cent. Certain boilers which are of 
the water-tube, internally-tired type, have 



BOOK REVIKWS 



2.19 



given the best results where ('(>., was 15 per 
cent., although in some types of water-tube 
boilers, when attempting to run at high 
values of C0 2 , the arches and side walls have 
been burned out. The correct percentage 
undoubtedly varies for different boiler settings, 
the quality of coal burned, etc., but a per 
centage of 10 to 12 per cent, usually indicates 
the most economical operation. The attached 
curve was taken from the Government 
Boiler Testing Plant at St. Louis. Mo., 
Bulletin No. 325 of the U. S. Geological 
Survey. This curve indicates that C0 2 
should have in general a value of about 10 
per cent. The upward slope of the curve 
indicates that a higher efficiency is obtained 
by raising the percentage of C( '._.. 

The improvement in boiler efficiency effect 
ed by increasing the percentage of CCh in 
flue gases from 6 to 11 per cent., as shown in 
this curve, is 11.8 per cent., and corresponds 
to a saving of 20 per cent, in the coal burned. 
This curve probably shows the improvement 
that could be expected in the average boiler 
plant. The percentage of C0 2 in the flue gases 
can be almost entirely regulated by proper 
damper control, careful firing, etc. 

In order to act intelligently, the boiler 
plant operators must have an analysis of 
the flue gases as often as possible. Due to the 
small percentage of CO compared with the 
total volume of flue gas, the usual gas analysis 
dues not give reliable figures on this content. 
The usual practice, therefore, is to obtain 
the percentage of C0 2 only. The oldest 
method of obtaining this analysis is with 
the Orsat apparatus, which is very reliable 
but not automatic. With this apparatus, one 
man who does nothing else analyzes a 
sample of the flue gases about every twenty 
to thirty minutes. Today there are several 
fairly reliable devices on the market which 
record the percentage of CO., automatically, 
giving the operator a continuous record to 
work by. 

A very satisfactory method is to have an 
automatic device before each fireman, This 
device need not have great accuracy, as 
anything that makes a mark varying with 
the tiring will constantly urge the man to 
his best endeavours. If, in addition to this, 
supervision is exercised by one well trained 
in the fireroom and the results for the day 
are accurately summated, a good degree of 

momy should be secured. 

It would appear that the curve can be 
taken to represent general values, although 



there is'no doubt that a few boiler tests on 
each type of boiler would indicate that the 
best results could be obtained by very slightly 
raising or lowering this curve. There can, 
however, be no question but that a pi ra 
as low as ti makes a tremendous different e in 
the economy of the boiler. 



BOOK REVIEWS 



THEORY AND CALCULATION OF TRAN 

SIENT ELECTRICAL PHENOMENA 

AND OSCILLATION 

By Charles Proteus Steinmetz 



McGraw Publishing Co. 



556 Pages 



Price Net $5.00 



The increasing use of the alternating current 
within the past few years has rendered the subject 
of transient phenomena of vital importance; there 
has been, however, no work available which treated 
the subject in a thorough and consistent manner. 
With the publication of Dr. Steinmetz's book, a 
treatise ha been placed in the hands of engineers 
which, for the first time, adequately di < u es these 
complex phenomena. The book is therefori 
pioneer work; it is, in fact, epoch making. 

An exact physical definition of the expn 

"transient phenomena." one which shall be iuffic 
iently inclusive and at the same time non-mathe- 

mat ical and easih undei I I, is rather difficult to 

frame. In his preface, the author defines the term 
le giving the common ch til of the phen- 

omena. He says: "the characteristii of all tran- 
sient phenomena is that they are transient functions 
of the independent variable time or dist 

Transient phenomena may be d IS all those 

phenomena that an i pi odial in charai er; i ... that 
begin at a certain moment or place and varj continu- 
ously either gradually or in an oscillatory mannei 
with the time o inally becoming 

COD tanl a1 a maximum or zero value. The building 
up of i i is a transient phenomena, I 

of current in a circuit upon closing tin' switch, the 
discharge oi a conden er. the surge in a traiis- 
i tC, ele. 
While the inherent nature Of thl 'i isoluti 

ly neo the employment of higher mathe- 

, ill,, ant li< i? « b.ere\ er p ed the 

I. a ,,i . | \ elop- 

ing the various I > applied them p 

cally to working condition . and has given coi 
numerical example-.. Tie pecially valuable 

, . n on 1 - inclusion of 

etical discu 
r , ,1,1,., , and '"nit the I- i fulness 

merely to those whose ma il training 

enabli to follow I la- i n : in their 



240 



GENERAL ELECTRIC REVIEW 



From such a mass of uniformly valuable material, 
■ ions for s] nment. 

The book covers the subject thoroughly, and con- 
phenomena as involved in gener- 
I incatii >n ami transm 
both normal and abnormal conditions. A 
beautifully lucid pn n of the subject of 

artificial leakage and loading is also included. 
I'., i and other propertii oi wires and cables 
arc fully discussed, i ighting 

and lightning protection. 



THE ELECTRIC SOLICITORS' HANDEOOK 

This book is issued by the National Electric 

Light Association under an editorial committee 

with Mr. Arthur Williams as chairman, and as 

might therefore be i roughly prac- 

1 and useful production. It is written for the use 

of central station i and all others directly 

interested in the applications of electricity. The 

book is divided into three chief sections, entitled, 

mating Engineering, Heating Engineering 

and Power Engineering." The three sections are 

prefaced by some valuable information on business 

ting and talking points. A complete index is 

provided which shows a very wide range of subji 

i; with. i of very concise ami simple 

and round numbers, etc.. is of course. 

ssary in a hook of this type, but it forms the 

addition to the library of the central 

'Hi man that we have had for a long time. 

The ■ he book can possibly he best illus- 

trated bj mples. The following, for instance, 

arc extracts taken tit random: 

n Service i d with 

Isolated Plant Hoi i Powei Required to Drive 
Mai him : Load Fai ti i I tifferent 

oi Service: Dai. II P sure Exhaust 

ot Motoi to Machine Tools; 
Power Taken by 
Different Heating Devi I imation of Illum- 

ination; The Lighting of I 

oi Lamp : Table of 
The Elei trii Motor in the 
Household; Tl I Coi pared with the 

and Gasolene Engine; Thi Ele< trii M 
1 with an Isolated Steam Plant; Electric 
Ivertising; Specifii Advantagi i trie- 

Light; The Relation of the Company to the Con- 
sumer; Mi ■ : Keeping I ! Ft. .; Ho\ 
in and Competition. 
would have beer -nil more valuable 
if it could ha time the 
manuscripts were completed by the different 

than two years ago — 
since it now contains a large amount of m. 
either no- available elsewhere or difficult to find. 

At the time referred to, it must have been a still 

exi eptional ion. We note with 

■ure that a 1 the credit of this 

production belongs to one old empl one 

present ei General t ompany. 



OBITUARY 

James J. Mahony, who had been connected with 
the General Electric Company since its organ- 
ization, died on March 19th at Holyoke. Mass., 
at the home of his sister. Mrs. A. J. McDonald. 

Mr. Mahony was born at Worcester, M: 
June Hi, 18(33. His parents were Maurice and Mary 
White Mahony. both of Ireland. 

He received his education in the Public Schools of 
Worcester, entering the Higli School in 1876, where 
he stood well in all his classes, and in particular 
showed marked ability in mathematics. 

At the end of his third high school year he left 
school to accept employment at Forehand & 
Wadsworth's pistol factory, where his father had 
been employed for some years. He remained with 
this concern a year or more and then served an 
apprenticeship as machinist with the McMahi 
& Carver Tool Company. During this time he 
took up the study of engineering and mechan- 
ical drawing. 

In the spring of ISSN Mr. Mahony entered the 
employment of the Thomson-Houston Company 
Lynn, where for the first six months he worked 
machinist under Mr. John Riddell, and was then 
transferred to the expert corps. A few months 
later he was sent to lake charge of the installation 
of car equipments and to supervisi thi operation of 
street railway apparatus during their trial period. 
While in this position he had charge of a number of 
important railway installations, among others the 
street railways of Albany and 'he original West 
End power station of Boston. 

In 1891 tin Foreign Department of the Company 
him 'o Australia to take charge of a number of 
installations, one of importance being the Sydney 
Tramways. 

Returning about two years later, he was p 
in charge of similar work m iut New York 

City. He erected tile electrical machinery in the 
Kent Avenue powi B lyn and built 

the first largi generators in bi 

Brooklyn and Boston. He also accomplished a 
grca ti work throughout 

the United States and Canada. 

About twelve years ago Mr. Mahonj became 

Connected with the Commercial Department of the 
New- York Office; and here, by reason of his tact- 
fulness, diplon unfailing courtesy, he made 
one of his greatest successes. 

In 1905, at the Company's request, he made a 

trip to South America, from which, after a few 

nths, he returned to his duties at the New York 

I Mice, where I d until the time- of his death. 

Through his inherent ability and by his own un 
efforts Mr. Mahon a high position in the 

electrical profession, his sterling character and 
perseverance commanding the respect and admi- 
ti of hi- He possessed a personal 

charm that w. nal. 

From his boyhood, he was very fond of outdoor 

ts, being particularly interested in ' md 

. he was also an exceptionally expert sailor ,.nd 

was the winner of a number of cups. He was a 

member of tin- Engineer' Marine and Field, Dyker 

Meadow, and Scarsdale Coif and Country Clubs. 

funeral services, which were very 1. 

attended, were held in St. Paul's church, Worcester, 
and the interment was ■ St. John's cemetery. 



FORMULAE. CONSTANTS AND HYPERBOLIC FUNCTIONS 

FOR 

TRANSMISSION LINE PROBLEMS 

With Explanation and Examples of their Use 

By M'. A'. Miller 



General Electric Review " Supplement 
May, 1910 



' offrighl 1910 



FORMULA, CONSTANTS AND HYPERBOLIC FUNCTIONS 

FOR 

TRANSMISSION LINE PROBLEMS 

Note. In using the formulae given below, the following points should be noted: 

All volt ayes given in the formulae musl I ie those I »e1 v een \\ ire and neutral. Thai is, I he line 
voltage for three-phase lines must be divided by \ •'! before substituting in the equation . 
must be divided by 2 for single-phase lines. The currents are given in amp wire. 11 

the power lost, delivered or generated, ealculated from the equations, only refers to one pha e and 
must be multiplied by 3 to obtain the total power in three-phase lines, and by '2 in the ease of 
single-phase lines. 

Phase Convention 

When the voltage is given at some point, as at the receiving or generating end, i1 is u u 
taken as the standard phase, and all other voltages or currents, calculated or given, refer to this 
phase. Thus, according to the sign convention adopted throughout viz, contra clockwise rotation, 
the given voltage v (say at the receiving end i is written ti without any j t erm. If the voltage or 
current at any point is a+jl>, the + sign indicates thai the voltage or current leads the 

voltage v by the angle tan -; a negative sign would show that they lag behind the voltages by 

the same angle. The form — a-\-jb indicates that the current or voltage at the point considered 

leads the voltage v. at the receiving end, by the angle tan I -I, that is, by an angle greater 

than 90°. 

A current or voltage a-\-jb means that a amperes or volts are in phase with the standard voltage 
phase and b amperes or volts are in quadrature with the standard phase. The prefix j is equal 

to\ - 1. therefore, jXj= — 1. The resultant value of voltage or current a ± jb = \'a i +b i . 

The product (a+jb)(c+jd) = ac—bd+j(bc+ad) and so on. For division , ., = '.,,,., and soon. 
1 J J J a -\-jb </- + /'" 

The cosine of the angle that the current leads or lags the voltage at any point is the ; 
or at that point. Hence, if the power factor is given (a1 the receiving end say) the currenl 

i = a±jb at this end can be obtained from the formula \ </'-'+/>-' ( /'/•' | j \ 1.0 /'/•"). Thusifthe 
resultant effective current is 100 ampere. a1 .80 P.F. lagging, i 100(.80 jyl.O 64) 
80 60; and must be substituted in the equations, in tin's form. 

l 

Constants m, m, and- . Tables II and III, Pages 6 and 7 

m. 

These are calculated to include the i i i.nd self-induction between win utral, 

d the resistance per mile of single wire, whether for three-pha e or ingle pha < lim 

When calculating single-phase lines, the constants determined for the wire spacings lyii 
a plane must not be used, but only those for triangular spacings. The constanl for p. icings in a 
plane musl only be used for three-phase lines, when a sufficient number of isil ions ha : 

made to produce balanced electrical conditions along the line. 

The constant for any wire spacings betw< o i iven can be readil] determined by 

■polation. As noted in the tables, the value for »i and - mu tb led b 1000. The 

m i 

values of m, .are correct as tin y stand. 

Resistance 

The' resistances included in the constants refer to hard drawn stranded copper wires, the 
value of the resistance used being given in the tables, [f the n isi tano o i iven line is slightly 
greater or less than that for which 1 e tables have been calculated, tb crease 

or decrea ;e in the constants can be obtained from Table I. page 5. 



.' "General Electric Review" Supplement 

Hyperbolic Tables. Tables IV to XIII, Pages 8 to 17 inclusive 

The values of cosh (x+jy), where x is given in the top row and y in the extreme left or right 
hand column will be found in the columns headed a and b, and the values of sink 
(x+jy) in the columns headed c and d. Hence, the value of cosh (x+jy) will be a+jb, and sink 
(x+jy) = c+jd. The values of these functions lying between those tabulated can be readily 
obtained by interpolation, see example A. 

Equations; 

The accurate equations for transmission lines are given below, provided the generator 
voltages and cum an simple harmonic functions of the time, and there is no corona effect. 

When the electrical conditions are given at the receiving end and £, = volts at receiving end 
between wire and neutral, /, the current per wire, c, the voltage at any point /, and i, the current 
at the same point. The distance / is given in miles and is measured from the receiving end, then 
e,= Ercoshml+Irmisinkml (1) 

i = I,coshml-\ — 'sinhml • 2 

»h 

If the conditions are determined at the generator end and £ s and I g are the voltaga and 

current respectively at this end, then the voltage and current at any point / along the line can be 

obtained from equations (3) and i4) following, / being measured from the generator end. 

e = Egcosh ml — I g misinh ml (3) 

i = 1,-coshml— -sinhml (4) 

W] 

Approximate Formulae for Short Lines 

These formulae can be used with an accuracy of 1 per cent, for lines using No. 2 wire up to 
120 miles long at 60 cycles and 150 miles at 25 cycles. Greater accuracy will be obtained if 
larger wires than No. 2 are used, though the difference is immaterial. See example B. 

If ;» = p+jq and the conditions are given at the receiving end, then 



(5) 



, =/•;,( \+ lHp \ y ® + jPqP\+I r m x l(p+jq) 

If the conditions are given at the generator end 

e = E B (l+- P '^ T ' + jPqPJ - 1, »',/( /> +jq l 7 

i=I l {\+ lHp l~ lf) +JPqP)-^Kp+Jq) 

A. Example of Accurate Solution 

Three-phase line, 300 miles long using hard drawn stranded copper wire No. 000 B.&S. 
triangularly spaced, with wires 10 ft. apart. Frequency 60 cycles. 

i)i 4-9 li; 12 44+ 485» 

Fromth '» ~ ' ~ Z~,l w, = 392 Ts.n/ — = " , ' J 

HIOO w, 1000 

Suppose the following conditions are determined at the receiving end. Line voltagi 104,000 
volts, or 60,000 vo wire and neutral. Load current 100 amperes at receiving end at 

.90 power factor lagging. Then, E r = 60,000 and ^ r =100(.90-j'\ l.o- !9~ s ) = 90-43.5;'. If the 

er factor had been unity / r =loo, or if .'.( leading ZV = 90+43.5/'. 

\-2\ +•> 1 1/ 1 :;n(i 
At the sending or genera d, ml = - =.126 +.633,/'. 

Then by interpolation from the tables of hyperbolics, the following values are obtained: 
cwAm/=cwA(.126+.633» = .812+.075;, 
sinhml =sinh(.l26+.633j) = .102+.597; 



"General Electru Review" Supplement 3 

The interpolation can be obtained as follov 

From the tables 

cosh{.\ 2 + .62/ ) = .821 1 + .071 \j 
cosh(.12+.64j) = .808+.072j 
Therefore, cosh\ .12+ .633; I = .8 L2 + .072j 

From tables 

cosk(.U+.62j) = .822+.081/' 

cosA(.14+.64/) = .810+.083j 
Therefore, coshi .11 .633./' I = .814 .1 182./' 
But cosh(.l2+.m3j) =.812+.072j 

Therefore, co5A(.126 + .633/') = .812+.075.;' 

By the same method sink(.126+ .633j) can be determined. The above steps, for obtaining 
the interpolations, were given more for the purpose of showing how to use the tables than for 
determining the values of the functions; since with a little practice, it will be found thai prad 
all values can be immediately obtained from th< abl bj inspection. 

Substituting in equation 1 1 1 the voltage at the generator end is given as follows: 

e g =60,000(.812+.075/) + (90- 13.5/) (392 -787) (.1024 .597;) 

= 48,700+4500j + 17,500+16,500i = 66,200+21,000 

Hence e =V66200 2 +21000 2 = 69,500 volts at generator end, between wire; ral. 

1 ''ID 
The generator voltage leads the receiving voltage by the angle tan . — =lan '.318= 1 i 

To find the current of the generator end, substitute in (2), then 
^(90-4 3 .5 i )(.812 + .075 i)+ 6Q - 000(2 - M+ S )( - 102 + - 597j - ) 

= 76.3-28.3j'-1.7+90.2j = 74.6+61.9; 

efore, generator current = \ 74.6 2 +61.9 2 = 96.8 ampi 

1 i;i .9 
The generator current, therefore, leads the voltagi a ' tan ' 

= tan l .83 = 39° 42'. 

Therefore, the current at the generator end leads the voltagi a1 thi - nen end b 

angle (39° 42')-angle( 17° 39') = 22° 03'. 

The power factor a1 the generator end 1 . therefore, cos(22° 03') = .927 leading. 

60,000 XI 00 X. 90 

Transmission efficiency is thus n = .81 

69,500 X 96.8 X. 92 1 

The total power delivered by the transmission line is 3> 60,000 ■ 90 16,200 kv 

er lost in transmission being 2,400 kw. 

To obtain the regulation, find the voltage at the generator end with no load current, thai is, 
/ -- 11. 
e g = 60,000 (.8 12 + .075.;') =48,700+ 1,500/'= 18,900 volts between win- and neutral. 

Hence.a voltage rise occurs between wires of 20,600 X V 3 volts = 35,500 voll erator 

end when the load is increased from nothing to ion amperes at .'.mi powi r fai tor l1 the 

iving end, with constant voltage at the receiving end. 

Since /, =(i at no load, the capacity current is 

. 60,000(2.44+.485;')(.102+.5977') ,,, ,. ,_ ,„, , 

».= ■ =90.2; — 1./ =90.2 amperes per wire. 

At no load, the voltage al the generator end lead ' the 

angle tan 'I - ' _ ) = /„;, i.093 = 5°19'; and the current a1 thegi ; ''"' 



'General Electric Review" Supplement 



receiving 



(Qfl ''\ 
' 'I J = tan -53.11=91° 04'. 



Hence, the current at the generator end leads the voltage at the generator end by the angle 
(91° 04') — (5° 19')=85° 45'; hence, the power factor at no load is cos(8o° 45') = .074 leading; 
and the total no load transmission loss due to capacity current is .074X3X48,900X90.2 = 980 kw. 

B. Example of Solution by Approximate Formulas 

Three-phase line 100 miles long, using hard drawn stranded copper wires No. B.&S. wires 
equally spaced in a plane and 8 ft. between wires. Frequency 25 cycles. 

In this case, suppose thai the generator conditions are determined, being 50,000 volts 
between wire and neutral, and 100 amperes per wire at unity power factor. 

Irom the tables m = -__.. ' to, = 470 — 254; — = .„..,, 

1000 w, 1000 

Therefore, ml at the receiving end is .0555+- 1025; and since ml = pl+jql 

therefore, pl = . 0555 and ql=. 1025. 

By substituting these values in formula (7), the received voltage is obtained 

e r = 50,000( 1 -'"'I' 4 + .0057./J-100(470-254;)(.0555+.102 
= 49,800+280/-5,200-3,420/ = 44 ) 600-3,140/. 

Therefore, the received voltage is \4 U'>m )- + :;, i in = 14,800 volts between wire and neutral, and 

/-314\ 
this voltage lags behind the voltage at the generator end by the angle tan 'I ^ IV) J 

= tan '(-.0704)= -4° 02'. 

The current at the receiving end is given bv substituting in equation (8) 
^=100(.996+.0057y)-^PMl^±^)(.0555+.1025i) 

= 99.6+.57;-.10-10.9i = 99.5-10.3y=100 amperes per wire. 

Therefore ,'the"current received is 100 amperes which lags behind the voltage at the generator 



end by th tanA nn '' J = «a» 1 (— .1035) = — 5' 

\ 99.5 / 



Hence, this current lags behind the voltage at the receiving end by the angle (5 55') 1°02') 
= 1° 53' and the power factor at the rei l ' 53') = .9995 lagging. 

Since the received current at no load ; s 0, the capacity current is given by the equation 



,(,+<">;-'" w)^,^,,, 



that is, capacity current or / at no load = .1(544- 10. ••/ 

. the capacity current is 10.9 amperes per wire and leads the voltage at the sending end by 

10.9 
the angle tan ' '.' =/</;; l 66.5= 89 ||s '. Thus the power factor at the sending end at no load is 

eos(89°08') = .0151. 

By substituting the capacity current or / at no load in equation (7), the voltage at the 
receiving end al no load can ined, and therefore the regulation at the receiving end between 

no load and 100 amperes. Substituting the vail 

e, = 49,800 +280j- (.164+10.9; 170 -254;) (.0555 • .102£ 

= 49,800 + 281 )/ + 363 - 572/ = 51 1,200 - 292;. 



"General Eleclru Review" Supplement 5 

Thus the received voltage is 50,200 volts, lagging by a small angle behind the generator 
voltage. 

The regulation at the receiving end is, therefore, 50,200- I 1,800 = 5,400 volts between wire 
and neutral, or betwen wires = V 3X 5,400 = 9,300 volts drop between no load and 100 amperes 
load at the receiving end, when the generator voltage is kept constant. 

Example of how to use Table No. I 

Assume that the No. 00 wire used in a transmission line operating at 25 cycles has a resistance 
of .423 ohms per mile, instead of .417 ohms as given in the tables for m, etc. 'Finn, in this case, 
the increase of resistance is 1.4' , nearly. Hence, the following changes musl be made in ;;;, m, 

and - in accordance with Table No. I. 
i'h 

The real term of m must be increased 1.4X. or , = \ :.V", nearly 

They term of m must be increased 1.4X.4% = 0.6% nearly 

The real term of m\ must be increased n.ii' , md the j term 1..'!' < nearly 

The real term of — must be decreased 1.4X0.2' , 0.39? nearly 

The j term of — must be increased L.4X0.3' , 0. I' , nearly. 

If the resistance were 1.4% less instead of greater, the values must be decreased where 
were increased in the above example and vice versa. 



TABLE I 



Percentage change of constants m, m, and — for change in resistance 

m, 

very 1', variation in resistance, change the real and j terms in the constants by the per© 

amounts given in the table. If the resistance is increa ed, the ign means, increase the term and ■ sign 
decrease the term. The opposite rule hoMs when the resistance is decrea ttiis table covers both 

methods of spacing and any distance between wires. 





R in 






60 


.. i 










25 CYCLl 5 








m 


m, 


m 


m, 






1 


B.&S. 


i Him . pur Mile 






Real 




Real 


j Term 


Real 




Reai 


j Term 










j Term 


: [\ rm 


Real 








+ 75 


None 














+ .05 


| .85 


.10 




230.000 




Xone 


75 


None 


+ 75 


i .85 


05 


• .70 


0000 


.263 


+ .70 


None 




+ .70 




70 


T.80 


.20 


+.20 


.80 


-.10 


5i, 


nun 


3 :n 


+ .70 


Xone 


None 


70 


None 


• .70 


.80 


+ .30 


.30 


| .80 


-.16 


• .35 


00 




.70 






70 


.05 


-.65 


-.90 


40 


• .40 


• .90 


-.20 


+.30 





.525 


• .75 


05 


• .05 


.75 


-.05 


■ .65 90 


■ .50 


+ .60 


: 90 


-.26 


• 15 







85 


+ .10 


10 


.85 


-.10 


+.60 70 


• .30 


30 


• 70 


-.26 


+.16 




- 


90 


20 


20 


• .90 


15 


55 50 


+.20 


+ .20 


• 50 


20 


10 



6 "General Electric Review" Supplement 



* TABLE II 
Values of m, m, and — per mile for triangular spacing at 25 and 60 cycles 



60 cvcles „°, 



I CLES , 



Spacing 

between Wires 

Inches 



72 
96 

120 
144 



Divide by 1000 

a &s. r ■ 



Divide by 1000 Divide by 1000 



Divide by 1000 



Spacing 

between Wires 

Inches 



222 'jhms per mile 



322 • 2 11 
306 -2 lOj 
294 | 2 09 
287 -2 09] 



346 -52 7) 
362 --52 7J 
376 -52 8j 
387 -53 1) 



2 82 -.429] 
2 70 - 394) 
2 60 - 365] 
2 53 ■ 347j 



KJ B.&S. R =.222 ohms per mile 



306-918) 
294 - 912j 
283 - 907) 
275 r 906] 



361 -120] 
377 -121] 
390 -122] 
401 -122] 



2 61 - 870j 
2 41 -772) 
2 33 - 730j 
2 27 691) 



72 
96 

144 



72 

120 

144 



No. 0000 B.&S. R =263 ohms per mile 



374 


2 llj 


352 


-62 2] 


2 76- 


486] 


357 


2 10] 


368 


-62 4] 


2 63 - 


445 


344 


-2 10) 


382 


-62 7j 


2 55 


418j 


334 


^2 09] 


391 


62 7j 


2 49 - 


399j 



N '1 10 B.&S. R =.263 ohms per mile 



362 - 932) 
337 - 927] 
326 922i 
316 915] 



372 -141j 
389 -141] 
402 -142) 
411 -142] 



2 35 - 892j 
2 26 - 822i 
2 21 - 780) 
2 17 - 749) 



72 
96 
120 

144 



00 B.&S. R = '(.i "hms per mile 



) B.&S. R =.33 ohms per mile 



72 
144 


467 2 12) 362 -78 0) 
437 2 12] 378 -78 0] 
421 -2 11] 392 -78 Oj 
408-2 11) 403-78 0) 


2 64 568) 
2 63 - 521j 
2 44 - 485j 
2 38 460) 


420 - 960j 
403 - 953) 
390 - 946] 
381 941) 


391 -171j 2 14 937] 
406-172) 2 09 885] 
420-173i 2 04 - 840) 
430 -174) 2 00 - 809) 


72 
96 

120 
144 




no B.&S. R =.417 ohms 


per mile 


00 B & S 

497-995) 
482 - 989j 
468 - 980) 
456-972) 


. R =.417 ohms per mile 

414 -207) 1 93 - 962) 
434-211] 186-907) 
445-213] 1 83 - 875] 
453 -213) 1 81 - 850) 




72 

II 

144 


556 2 16) 372 -97 01 
536-2 14) 391-97 8i 
617 2 13) 405 -98 lj 
504-2 13J 414 98 2] 


2 52 652) 
2 40- 600] 
2 33 565) 
2 29 - 545] 


72 

120 
144 




B.&S. R = 5! 


per mile 


No li B &S 


as per mile 




144 


678 2 18) 385 120] 
663 2 17] 402 -121) 
633 2 16) 415 -121) 
615 2 15) 424 -121] 


2 36 - 737) 
2 28 • 685) 
2 22 -649] 
2 17- 622i 


591 -1 05] 
569 -1 03) 
554 -1 02] 
641-1 01] 

BSS 


446 -260) 1 71 960] 
458 -253] 1 67 924) 
470-255) 164-892) 
479 -256) 1 62 • 866] 


I'.l 
1 20 
144 




No 1 B &S. R =665 ohms 


per mile 


R =.665 nhms per mile 




96 
120 

144 


825 2 23. 403-149J 
791 2 21i 418-149) 
766 | 2 20) 430 - 160i 
749 • 2 19] 441 -151j 


2 17 - 803] 
2 11 755) 
2 07 r 725) 
2 03 69Sj 


691 110) 
670 - 1 09j 
655 -108) 
640 -1 07j 

No. 2 B AS 

800 - 1 17j 
779 1 16) 
756 1 14j 
744 1 14] 


476-300] 1 51 - 946j 
495-304J 147-901i 
507 -307] 1 44 - 873j 
516 -309) 1 43 • 855) 

. R =.835 ohms per mile 

518 -354) 1 31 896] 
536-360] 1 28 - 861) 
548 362) 1 27 - 840] 
559 -364i 1 26 - 821] 


72 
96 
120 
144 




II.&S. R-.S 


per mile 




72 

N 

120 

1 11 


989 2 29) 422-182] 
945-2 27) 438-182) 
920 2 26i 460 -183) 
905 -2 25j 460 -184) 


2 00 - 860) 
1 94 | 810) 
1 90 - 776i 
1 88 • 751] 


70 

96 
120 

144 



* This table can also be used for single i 



'General Electric Review" Supplement 7 



* TABLE III 



Spacing 
betweei 

Inches 



60 c\. 



LBS o o o 



96 
120 
144 



96 
120 
144 



72 
96 

120 
1 44 



7U 

96 

!0 

144 



Dividi 

00 B.ftS~ 



m, _j_ 

m, 
Di\ 

mile 



m 



96 
120 

144 



310 J.Hj 
297 -2 11. 
■286 —2.101 
278-2.09) 





■ i B.fts! 



■ 

in. 



360 -52.8] 
376 -52.8J 
388 -62. 9j 
397-52.9] 



Divi 
■222 ohms pei 



2-71 - 398; 
2.60-366) 
2 53 -.345j 
2.47 .329j 



' IZ-&S S 21 ...hms per mile 



296 ■ .917) 
284 -.913] 
275-910] 
268 ■ .909] 



375 121j 
390-121 6j 
404-122J 
415 122j 



72 

96 

120 

144 



■361 -2-llj 

■ 346-2.10] 

■ 332-2.10) 
324 -2.09J 




241 -780j 
234 .729) 
2 27 -.687) 
2 22 .654) 






2 65 ~.463j 
2.57 -.422) 
2.47 -390j 
241 -.373) 



« P^r mile 



ims per mile ~ 



340-929) 
326 .924) 
315-920) 
308 917j 



386-141) 
401 -142) 
416-142 6) 
426 143) 



2 29 - 840j 
221 , .785) 
2 16 -.742) 
2.10 | 706) 



439 -2.12) 
421 -2.12) 
406 -2. Hi 
396 -2.11J 



374-77.4) 
390 -77.6) 
405 -77.9) 
416-78.0) 



2.56 -530j 
247+491) 
2 38 - 457i 
2 32-434) 



per mile 



N B.^R-,417 ohms per mile 



406^.955) 
391 - 949j 
■379-943) 
370 -939j 



406 -172) 
420 -173) 
434 174. 
445-175] 



2 10 -.894) 
2.06 -.846) 
1 98 ^797j 
196 - .766, 



540 2.16] 
■519 -2.15] 
■500 -2.13) 

487 +2.12) 



388 -97.0J 
403-97.1] 
416 -97. 5i 
425 -97.5] 



2.42 -.605) 
2.35 -.666j 
2 27 -632j 
2 23 - .612] 



N °- °° B -*S R nr,.h mS per mile" 



No, B.&S. R = 525 ohms per mile 



484+.990J 
469 1.984) 
456 -.977] 
447 -.973] 



426 -208j 
443 -211] 
468 -214j 
467-216J 



1.89+924] 
1 84 .877) 
1-79-838) 
1 76 l 812j 



657^2.18] 
630-2.17] 
■ 609-2.16J 
595 -2.16] 



398 -120.0] 
416 -120.5] 
428 -121.0) 
439-121.0) 



No B.&S R = 525 ohm 



2.30 - .696) 
2.22+646] 
2.16 -6Hi 
2.11 -.686] 



No 1 BK R=. 665 ohms per mile 



673 1038] 466-261) 

555 -1.025J 470-264 

542-1.020J 486-267 

530 l.Ollj 496-260 



1 68 t .930] 
1 66 H .880* 
1 61 ■ .864) 
1.68 + .830J 



802 -2.23) 
769 2.21J 
745 -2.20) 
726 -2.19] 



418 -160 0] 
432 -160.0) 
445 -150.5] 
456 -161.0] 



ll.&S R= 665 ohms per mile 



2.12 - .760; 
2.06 ^.716] 
2 02 -682j 
1 95 • 654j 



N " " B&S R = 835 ohms per mile 



673 1 096j 493 -303i 

.656+1.084] 509-307] 

638-1.070) 620-309 

625 1 064] 631 -312j 



1 466 t 902) 
1 440 -.868] 
1 420 ■ 846, 
1 396 -.820] 



No 



72 

120 

144 



959 2 28, 435-183) 

f" 2 27, 452-184 

■898-2.26) 465-185 

8812.25J 476-186 



i mile 



1 96 -820] 
1-88 - 770j 
1 85 739i 
1-82 : .712) 



• 780 t 1.160] 
■759+1.160] 
711 1.135) 
729 1,127; 



532 -368) 
660 -363] 
662 -366) 
570 -369) 



1290 .870] 
1 266 < 836) 
1 250 - 814i 
1236 • 800j 



72 

n 
120 



120 

141 



120 

144 



72 

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11 General Electrii Review" Supplement 13 



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1159 202 
1.151 215 
1.143 .228 
1 135 241 
1.126 .254 


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"General Electru Review" Supplement l-~> 



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622 1 050 
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480 1.096 


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130 1.314 
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183 1.307 
207 1.303 
234 1.299 


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1.261 
1.252 
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1.234 

1.225 


1.215 
1.204 
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1.182 
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1 159 
1 146 
1.132 
1.118 
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999 .537 
982 .550 
965 .562 
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00 00 00 CO CO 




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eg -4) to oo o 
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00 00 00 00 00 


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w4 

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CO 


























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CM Tf to CO O 

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t- 

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00 t- t- t-P- 


736 1 
721 1 
705 1 
689 1 
673 1 


666 1 
639 1 
622 1 
60S 1 
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o 
t- 

tO 
















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t- p-t- 00 CO 


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CM CO tO tO t— 
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tO tO IO -f CO 
CO CO CO CO CO 



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1 — c 








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— 1. 




-A, 




=J 





FTr* 




VOL. XIII, Xo. 6 



Copyright. 

■'. patty 



JUNE, L910 



CONTENTS 



Editorial 



243 



The Single-Phase [nduction Motor, Pan II 

By Profs. J. II. Morei kiii i \M) M . Aki \ih 



245 



High Speed Motors for Wood Working Machinery 

]'.\ John Liston 



251 



Commercial Electrical . Part X" III 

By E. P. Collins 



259 



Hyperbolic Functions and Their Application to Transmission Line Problems, Pari III 

B\ W. E. Mll.LKR 



264 



Electricity in The Mines of the Davis Coal and Coke Company 

By R. Neil Williams 



26S 



The 1200 Vol1 Railroad A Study of its Value for [nterurban Railways 

By Charles E. Eveleth 



Small Buffing and Grinding Motor Drawn Shell 'i 

B\ R. E. Barki i 



2S2 



Gears for Motor-Driven Tools with Special Refi ibric Pin 

By [ohn Riddi i i 



2S4 



Annual Ri o he Gem ra] Elecl rii l o 



JSli 




Group of Two-Spindle Shapers Driven by 5 H.P. Induction Motors 

Htywood Bros, fit Wakefield Company, Gardner, Mass. 

(See page 2 I 




THE 1200 VOLT RAILROAD 

The transportation facilities of a country 
are an accurate criterion of thai country's 
condition; no form of public improvement is 
reaching in its effects than arc the 
improvements in these facilities. For this 
reason, the use of electricity for transporta- 
is probably of more importance to the 
public at large than any other application oi 
this form of energy. 

In the building of an electric road or the 
electrificati i oi a -team road, one of the first 
matters thai requires consideration is the 
choice of the system to be employed. At the 
present time this choice is practically con- 
fined to the 600 volt and the 1200 volt tor 
higher) systems with the direct current, and 
ingle-phase (15 or 25 cycl I and the 
ttrei phase systems with the alternating cur- 
rent. In any case any one of these would be 
entirely operative, and each has its specific 
advantages. The selection is therefore a 
matter calling for the highest engineering 
abilit; ; the ability to weigh the several ad- 
vantages and disadvantages of the different 
con idered in relation to the condi 
of the specific case in mind, and to 
one which, all things considered, 
[uiremenl 5. For, while da1 a 
ing roads are not lacking, the local 
condition nude,- which the roads opt 

I ant a bearil g upon t lie mat ter 

idify any conclusions that 

might he drawn from such information. 

, it is difficult or impossible to con 
the different systems l>y means of the data 
taken from different roads, 'he local condi- 
; Mm/ dt imilar. 

( )n accoui t of t!i ortai i 

the subjeel . authoritative an icle i hal help 
to determine which oi VStems is 

o pari icular field ari oi much 
inter- 

In th- Review for June, 1909, an at 
by Mr. G. II. Hill was published, compa 



the 1200 volt direct and the single-phasi 
alternating current systems, and showing the 
advantages of the former for a certain cla 
of interurban service. At that time, it was 
pointed out that, whereas the chief claim of 
the single-phase system for recognition i- the 
low first cost of the distributing system, this 
saving is obtained at the expense of much 
complication of the motor car equipments, 
oil switches being necessary to control the 
circuits, a heavy transformer to supply the 
low potential, and an additional winding being 
required on the motors to make commutation 
possible. Both the first cost and the main- 
tenance charges for these equipments are 
therefore considerably greater than the cor- 
responding items for the L200 volt system. 
Again, on account of inductive drop in track 
and line and the starting characteristics of 
the single-phase alternating current motor, a 
much higher potential is demanded than in 
'he case of the 1 I'll! I volt system, for the 
same operating results. 

Mr. Hill summarizes the situation as fol- 
lows: "All things considered, the avi 
interurban road will cost less to install, will 
he operated for a less amount, and will give 
a more reliable and satisfactory service when 
equipped with L200 volts direct current than 
it will with an alternating current system of 
6600 or i L000 volts." 

In the pre allt issue of 1 In Ul \ II W WC 

print a paper on The L200 Volt Railroad. 
which w.i read by Mr. Charles E. Eveleth 

tin- Philadelphia sectionof the A. I. I'M'!.. 

and whicl ics the 1200 and lit II I volt 

current systems. Mr. Eveleth indi- 

i clear! to lervice for which the 1200 

volt system is particularly adapted. He 

i hal 'he adopt i. ,ii of this system not 

only largely dei , through 

ond- 

di tribution conductor . I" 1 reatly 

fewer ' he power 



- 



GENERAL REVIEW 



consn- 

ngacorr-:-: odii 

consider 
- 
_ 
cm 6* • Ed on 

the lov 

econoir 
- ~ ■ red with 

- 
i 

here are nea- 

nd ova 



r.CTRIC HAULAGE IN COAL 

-.troducc 1887 

- 
r 

«al mine 
i 



fined 

ised, 

i 

- 



i 



- 

trial accom- 

par. id adoption 

on ace 
iges. 

- 
I ■ ■ 

Review. Mr. R. N 

are 
■ 

eh. 
i 
-" 

r " " m ....... _ 

opt' 

ger hauls at high 

as -o doing will require 

- 

lif- 
rent pr 

sed and the rea- 
lained. 

■ 
i 

■ 

Jed 

. 

Review 
' -• 
W. 



245 



THE SINGLE-PHASE INDUCTION MOTOR 

Part II 

By Profs. J. II. Morei roi ■ i and M. Arendt 

Columbia Universi 1 v 



Characteristic Curves 

The preceding torque equation, while 
valuable in that it indicates the general 
characteristics of single-phase indu 

motors, is not readily applied to the detail 
study of any specific machine. The working 

ely determined bj 

actual test. They may, however, be derived 
with moderate accuracy by means of a circle 
diagram somewhat similar to that utilized in 
connection with the study of the polyphase 
motor. 

The particular diagram described herein 
(Fig. 7) is that developed by A. S. McAllister. 
and its construction is as follows:* 

Let the vertical line OE (Fig. 7) represent 
the line voltage. Draw at their proper phase 
positions and scale values the no-load as 



well as the locked currents OM and OF 
lectively. 
.1/ V ami IF represent the energy com- 
ponents of the corresponding currents and 
are therefore directly proportional to the 
respective inputs. Through .1/ draw a line 
.l/A' perpendicular to OE, join .1/ and /•'; 
draw also a line perpendicular to the middle 
of ME intersecting MK at A'. With A as a 
center and cither XM or XF as a radius 
describe the circular arc MPF, this being the 
locus of the primary current. The distance 
IG represents the added primary or stator 
loss existing with 1 he rotor locked, its length = 
(added primary copper loss -f- total locked 
watts) X ///•'. Draw the line GM. With this 
construction completed the performance of 
the motor may be determined l>y inspection. 




Fig. 7. McAllister "irele Diagram for a 10 H.P. Single-Phase Induction Motor 
•■mating Current M • McGran I 



246 



GENERAL ELECTRIC REVIEW 



For example, the factors determining the 
performance of the motor with a current P 
are as follows : 

OP to scale represents the primary current. 
cos Poll is the power factor of current <>/'. 
/'/ repri ents the watts input at current 

OP. 
.l/.\ the watts input at no load. 

TQ n presents the watts loss at current OP. 
I R represents the total primary loss at 

current (>/'. 
QR represents the added secondary copper 

loss. 
QP n ■ •- he watts output at currenl 

or. 

QP-i-PT represents the efficiency of the 
moti rent OP. 

l'o-\- PR ents the per cent. slip. 

7.05 QP+T.p.m. represents the torque at 
current OP. 

The field set up through the motion of the 
varies as the speed w, consequently 
the torque T for a given rotor input II"' will 
be proportional to the product of w II'', or 
T=Kiu>W. (19) 

The torque, however, is also proportional 
to the secondary output II'" divided by the 
speed <o, or 

T=K t (W'.'+ a ) 
whence 

co=K(W" + W' . 20) 

The secondary input, from the cir- 
cle diagram, is proportional to PR; 
the output is similarly represented 
by PQ quently (PQ-i-PR.)* cor- 

responds to the rotor speed as above 
stated. 

The diagram shown in Fig. 7 has 
been applied to the determination of 
the characteristic curv ■ andard 

220 volt, 60 cycle, I pole, L0 horse- 
power single-phase induction motor. 
The fundamental data employed in 
the construction of this diagram were 
derived by test, and are . 

ir resistance .304 ohm, current 
with motor running fr< 

ling input 1 kw., and power 
factor 'J I percent. The current with 
standstill is 17n amperes, 
input 13. I kw.. p 

. Line potential in both instam 

1- 220 volts. 

- values derived from the diagram are 

given in Table I and presented in the form 
of curves in Fig. 8. 



Comparison of these characteristic curves 
of the single-phase induction motor with those 
of the standard polyphase induction motor 
brings out the fact that the former has zero 
torque, not only at synchronous speed but 
also at standstill, whereas the latter has a 
starting torque in excess of that developed 
at rated li tad. 

Table II gives characteristics of operation 
attained by standard single-phase induction 
motors. 

Comparison of the values in this table with 
the characteristics of polyphase induction 
motors shows that in general the power 
factor, efficiency and pull-out torque ate 
higher for polyphase than for single-phase 
motors, while the speed regulatii in of the single- 
phase machine is better. This latter featuri 
the single-phase induction motor is accounted 
for by Dr. C. P. Steinmetz as follows.* 

ingle-phasi ne primary ami 

a multiplicity of secondary circuits exist, all second- 
ary circuits arc to be considered as corresponding 

to tin' same primary circuit. Thus the ioint 
impi all secondary circuits must be used 

as the secondary impedance, at least at or near 
synchronous speed. Thus, if the armature has a 
quarter-phase winding of impedance /£, per circuit. 

the resultant secondary impedance is ~'; if it con- 
tains a three-phase winding of impedance Z, per 

/ 
circuit, the resultant secondary impedance is ''. 

3 




10 



40 45 50 



FiR. 8. 



15 20 25 30 35 
Ft. Lbs. Torque 

Characteristic Curves of 4 Pole. 10 HP.. 220 Volt, 60 Cycle, 
Single-Phase Induction Motor 

In consequei iltant impedam 

a single-phase motor is less in comparison with the 
primary impi han in the polyphase motor. 

Since the < lr< ■!> in speed under load depends upon 

'Elements of Electrical Engineering 



SINGLE-PHASE IXI.H'CTIOX M( >T( >R 



247 



tin- sei i mdary ri ease in sj u 

the case of the single-phase motor is generallj less 

than that in I motor." 



branches, one of which is inductive and the 
other non-inductive, [f supplied with two- 
phase currents, even though these be less than 
90 degrees apart, an induction motor is self- 
starting; thus when synchronous speed is 
approximated, the pha le iplil I ing device may 
be cut ou1 and the machine will continue to 
operate. There arc many other ways to 

TABLE I 

CHARACTERISTICS OF A 220-VOLT, 60-CYCLE, 10 HORSE POWER, SINGLE PHASE 

INDUCTION MOTOR 



Methods of Starting 

As already shown, the simple single phase 
induction motor cannol exert any starting 
torque. In practice, however, except in the 
smallest sizes which may be started bv hand) , 







' 


' , P.F. 
24 


Kw. I 


1 lutpul 


K fi- 


R.F M 


Torque 




.1/ 


Pi 


1 


II 


ll 


1 81 ii i 


II 




1 


25 


65 


3.56 


3 l 


7(1 


1 7S2 


10 




2 


30 


i .i 


1.95 


5.03 


,(', 


1772 


15 




'■> 


411 


81 


7.15 


7.65 


80 


1760 


23 




P 


.-,(1 


83 


9.24 


10 


81 


17 17) 


30 




• ) 


60 


85 


ILL' 


12 


80 


1 738 


36 




6 


80 


81 


14.2 


1 1.7.", 


7.S 


1715 


47) 




i 


100 


78 


17.2 


16.5 


72 


1690 


51 




8 


119 


711 


l.s. 7 


16 


64 


L640 


51 




9 


140 


61 


18.8 


13.1 


52 


1550 


14.5 




in 


1 55 


:,i 


17.6 


8.8 


37.5 


14011 


33.0 




F 


170 


36 


13.4 


" 





o 






the conditions of service which this motor is to 
meet require a starting torque as high as 
150 per cent, of the rated value; consequently 
some device to produce this feature must be 
connected with or incorporated into the 
machine. The methods of accomplishing 
this result may be grouped into two general 



obtain such two-phase currents. The two 
parts of the circuit may be in series, one 
being shunted by inductance or capacity 
(Fig. 9). They may also be put into induc- 
tive relation to each other to produce a 
phase difference. 

Motors employing the above starting 



TABLE II 

DATA OF STANDARD SINGLE-PHASE INDUCTION MOTORS- 



110 TO 440 VOLTS 



HP. 



1 
2 
5 

10 

20 
30 
50 






Percent. 

Slip 



Pull-out 



PER CENT. POWER FACTOR LOAD 



PER CENT. EFFICIENCY LOAD 




46 


58 


55 


7,11 


56 


65 


78 


83 


, ."] 


81 


78 


80 


68 


80 


m 


94 



♦Pull-out torque in terms of rated load ton 

The first is technically known as 
phase-splitting and the second as the repulsion- 
motor met hod. 

Split-phase Starting 

Two phasi i in e be obtained i in 

a single-phase circuit by dividing it into two 



Rid. 


U 


i 


1 


Rtd. 


H 


66 


68 


53 


60 


63 


60 


73 


t 5 


60 


63 


68 


62 


1 1 


76 


71 


, .i 


78 


* t 


86 


86 


71 


70 


7 » 


70 


84 


83 


i ."> 


79 


80 


70 


86 


87 


85 


88 


86 


85 


85 


84 


f 1 


81 


83 


82 


93 


in 


82 


SI 


86 


so 



methods are provided with two stator wind- 
ings, a working winding and a starting winding. 
The i wo winding are di placed from each 
,i It, r by aboul ninel y i Ii ctrical di 
just as in the ordi 
The working winding, however, i of mure 

U.S. Pal 



2 In 



GENERAL ELECTRIC REVIEW 



turns, being spread over a larger surface, and 
is of heavier wire than the starting winding, 
because it remains in circuit as long as the 
motor operates, whereas the starting coils 
only in use momentarily. 



Fig. 9. Split-Phase Circuit, using Resistance 
and Inductance 

The method illustrated in Fig. H) has been 
developed by Brown. Boveri and Co. of 
Baden, Switzerland. At starting, the two 
windings are placed in eries across the supply 
lines, the starting winding 5 being shunted 
by the condenser. The current consequently 
lags more in that winding, the difference in 
pha :e between the currents in A' and S being 
sufficient to set up an elliptically formed 
rotating field. The starting winding and its 
condenser are cut out and the working 
winding placed directly across the line by 
the double-throw switch '/'.when 
the motor has approximately attained syn- 
chros This method is slightly 
modified when machines of over 5 h.p. 
city are to be started. The two windings 
are plai i larallel, as 
shown in Fig. 1 1. By this means the working 
coil circuit is not broken and the I' 
ring upon cutting out the auxiliary winding 
minated. 

An excellent method for starting single- 
phase motors has been developed by the 



General Electric Company under patents 
granted to Dr. C. P. Steinmetz, the con- 
nections for which are shown in Fig. 12.* 
Two terminals of the stator winding, which is 
substantially of standard three-phase con- 
struction, are connected directly to the supply 
lines. The third terminal is also conn 
to either one of the mains through an auto- 
transformer, the order depending upon the 
direction of rotation desired. The ends of this 
compensator are placed across a condenser. 
This combination is technically known as a 
condenser-compensator . and is employed be- 
cause a condenser of given volt-ampere 
capacity is more economically constructed 
for high than for low voltage. The starting 
winding can be cut out by opening the switch 
at 5 after the motor is up to speed. It may, 
however, be advantageous to keep the 
starting coil in circuit, if of sufficient current 
capacity for continuous service, because the 
increased power factor at light loads thus 
obtained more than compensates lor the 
losses occuring in the transformer. 

The use of external phase-splitting appa- 
ratus may, however, lie dispensed with if the 
two stator windings are arranged to have 
different time constants. This is accomplished 
by having the auxiliary winding of larger 
self-inductance than the main coil. Hcyland 
devised a very successful motor of this type, 
utilizing the scheme suggested in the Tesla 




Fig. 10. 



Connections for Starting Small Single-Phase 
Induction Motors 



patent cited above. The working winding /' 
is distributed in a scries of semi-closed slots. 
The starling coils .V are short-circuited upon 
themselves and placed in closed ducts, the 
result being a highly inductive secondary 
circuit, the general arrangement of which is 

60 ! 9 !0 ■ A "" B98 



SINGLE-PHASE INDUCTION MOTOR 



249 



illustrated in Fig. 13. The current induced 

in the secondary winding lags almost 90 

degrees with respect to thi . current, 

icing a field component similar to that 




Fig. 11. 



Phase Splitting Method Devised by Brown. Boveri 
& Co. for Use with Large Motors 



caused by the second phase of a tw 
current. The starting torque thus produced 
is large, though the power factor of the 
machine is necessarily low, and therefore the 
starting coil should be cut out as soon as the 
machine has come up to speed. * 

The rotor windings employed in connection 
with any or all of the preceding method for 
ng may be of the standard squirrel-cage 
or slip-ring type. 

Repulsion Motor Starting 

A very interesting type of self-starting 
single-phase induction motor is one that is 
provided with an armature of the ordinary 
direct current drum type, having a disk com- 
mutator with radial bars.t The brushes bear- 
ing upon the commutator are di placed aboul 
!■"> degrees fro corresponding neutral 

zones and short-circuited upon each other, 
•at or winding is connected to the supply 
lines, and at I arting the machine speeds up as 
a repul "hi : oti >r. In the anm 
tweer id the shaft an 

governor Mich are i 

outward, furl her and further, by centr 

machini When 

synchronous nearly attained, the 



force acting upon these weights is sufficient 
to push the heavy copper ring R, against the 




[- 



il 



d^± 



\ 




w 



Fig. 12. General Electric Company Condenser Compensator 
Method of Starting Single-Phase Motors 

action of spring .S', into contact with the 
inner cylindrical surface of the commutator 




V..! XXXVI. i 






Arrangement ■ •(" Working and Auxiliary Stutor Coils. 
Hcylancl Self Starting Single-Phose Indur ion MotOI 



250 



GENERAL ELECTRIC REVIEW 



bars G, thus completely short-circuiting the 
armature winding. Simultaneously with this 
action the sleeve P is forced to the left suffi- 
ciently to lift the brushes B from the corn- 




Fig. 14. General Arrangement of Wagner Motor, Showing Automatic Short 
Circuiting Devices 

mutator. This series of automatic actions 
transforms the machine from a repulsion toa 
single-phase induction motor, having in the 
latter form what is substantially 
a squirrel-cage armature wind- 
Tin tarting torque thus 
obtained may be readily ad- 
justed to about twice the nor- 
mal value, without an excessive 
current being required. 

A very interesting feature 
of this motor, and one equally 
pertinent to repulsion motors. 
is the relation between torque 
and thickness of rotor bru 
The series of curves shown 
in Fig. 15 were determined 
from of a 5 h.p., 220 

volt Wagner motor. Curve .1 
the speed torque relation 
on ;i ing with normal 

brush thickness, this being 
substantially that of a com- 
mutator bar. Curve A' rep- 
LtS the relations existing 
with a brush of twice m 
thickness, etc. It is apparent 



from these curves that the normal thickness 
of brush gives the highest starting and syn- 
chronous speed torques. Further study of 
Fig. 15 indicates that use of a brush thinner 
than normal might tend to 
produce starting and syn- 
chronous speed torques of 
greater value than occur with 
normal brush thickness. Prac- 
tical questions, however, as 
regard mechanical strength 
limit the reduction of brush 
thickness. 

Single-phase induction mo- 
tors, in addition to being 
provided with one or another 
of the preceding means for 
developing starting torque, 
require, when above moderate 
size (3 or 5 h.p.), the in- 
troduction of starting 
compensators, or the use of 
wound rotors with slip-ring 
control. This precaution is 
necessary as the inrush of 
current otherwise occurring 
would be considerable and likely to react 
upon the line, producing voltage fluctu- 
ations. 




600 800 1000 1200 1-100 1600 1800 
R.P.M. 



Fig. IS. Speed Torque Curve with Various Brush Thicknesses 



1'.-. 1 



HIGH SPEED MOTORS FOR WOOD WORKING MACHINERY 

Hy John Lis n i\ 



The specialization to which the construe! i m 
of modern wood working machinery has been 
subjected in order to obtain results commen- 
surate with the improvement in the me- 
i hanical equipment of other industries, has 
tended to concentrate the attention of 
practical operators of wood working ma- 
chinery on the various factors entering into 
the power eosts of pro'luct ion. 

The rapidly extending use of motors in 
practically every industry indicates that the 
superiority of the electric drive as compared 

with mechanical drive for application to all 
forms of machinery is now generally acknowl- 
edged, and a discussion of the relative merits 
of the two methods in the present ease is 
unnecessary. 

The system of motor drive adopted, 
however, directly affects the percentage oi 
the initial power which is actually applied at 
the machine, as well as the speed of operation, 
the cost of installation and the amount of 
floor space required. The problems to be met 
by the manufacturers of wood working 
machinery and those specializing in electric 
motor applications, will, in the future, deal 



largely with the question of obtaining the 
highest possible efficiencies for each given set 







Fig. 2. 




Fig 1. 7 12 H.P. Induction Motor Direct Coupled to Two 20 in. Circular 
Cross Cut Saws 



3 4 HP. Induction Motor with Spindle Chuck 
Mounted on Motor Shaft 



of operating conditions rep- 
resented by the varying 
demands peculiar to the 
industry. 

The relative values of 
group and individual drive 
urn .1 lie determined in every 
instance by a careful analysis 
of the requirements oi the 
installation, and while there 
are many successful examples 

of economical group drive, 

it is now the com 'en us of 
competent opinion thai in a 

majority oi ca e 
highest efficienc} . both Eoi 
machinery to be driven and 
for the electrical equipment, 

can lie lies! Ob 

1> y the applicatio n 

io each 

unit. Tlii i i ill) true 

where the operation ol the 
machines is intermittenl , as in 

OSl oi current, 
if obtained from an "in i I. 



GENERAL ELECTRIC REVIEW 



source, is entailed only during the actual 
operation of the machine, so that by the use 
of instruments the actual cost of the current 




Fig. 3. 



1 H.P. Induction Motor with Dowel Cutting 
Saw Mounted on Motor Shaft 



consumed by each machine or group of 
machines ran be accurately determined. 

If. <ni the other hand, the plant utilizing 
motor drive is provided with an isolated 
generating outfit, the si/.c of the prime mover 
and generator, as well as the power factor in 
the case of alternating current 
plants, will be appreciably 
affected by the choice of group 
or individual drive. In the lat- 
ter case, each machine can lie 
equipped wit li a iiu iij ir which 
will most nearly meet the 
exacl requirements in regard 
to i he maximum desirable 
Speed and the amount of power 
delivered a1 the driving shaft. 

Where the operation of the 
\ arious unit s is intermitto 
the individual drive system 
will, in practically every case, 
permit the successful opera 
tion of a plant when equipped 
with a much smaller geni 
ating i 'in ti; t han would be n 
quired with motors driving the 
machinery in -roups, even if 



there is considerable variation in the length 
of time that the units are in service; for, in 
the latter case, power is wasted through the 
unavoidable operation of shafting and belting 
which, during varying periods, performs no 
useful work. 

There is perhaps no industry in which the 
electric motor has been so successfully 
applied as in that of wood working. This is 
due to the fact that the average wood working 
machine operates at relatively high speed, and 
therefore lends itself readily to the most 
economical application of the electric motor; 
i.e., by direct connection to the driving shaft 
of the machine. 

In designing motor drive for wood working 
plants, there should be active co-operation 
between the manufacturers of wood working 
machinery, the practical operator, and the 
designing electrical engineer, to the end that 
each individual machine may be constructed 
and operated as a compact, self-contained 
unit capable if positive and ready control by 

the class of labor generally found in w I 

w< irking plants. 

In order to obtain the high speeds required 
for the application of individual motors to 
wood working machinery, practice has in 
many instances included the use of short 
belts between the motor pulley and the 
driving shaft of the machine. It was with 
the object of eliminating this characteristic 
feature of mechanical drive that the General 
Electric Company developed its line of high 
speed motors designed for coupling direct to 
the driving shaft . 




Fig. 4. 5 H.P. Induction Motor Direct Connected to Driving Shaft of 
6-Spindle Automatic Dowel Boring Machine 



HIGH SPEED MOTORS FOR WOOD WORKING MACHINERY 



253 



As a large majority of the operations 
carried on in wood working plants demand 
constant speed, and as the characteristics 
of the induction motor render it especially 
suitable for constant speed work, it was de- 
cided to adopt the three-phase induction 
motor as a standard type for this service 
in those places where alternating current is 
available. 

This motor is compactly and strongly 
constructed, its rotating element being as 
simple in form as the ordinary hanger bearing; 
and, as it has no commutator, its operation 
does no1 involve any fire risk and the motor 
may therefore be safely installed in wood 
working plants without being enclosed. No 
special foundations are required and the 
motors may be mounted on the floor, wall or 
ceiling, or on the framework or headstock of 
the wood working machines. 

The use of high speed motors in wood 
working plants is not merely a question of 
power efficiency, but one of economy in the 
cost of equipment, and for this reason should 
receive the careful consideration of all persons 



interested in increasing the volume and 

lowering the cost of production in this indus- 
try. By the adoption of high speed motors, 





Fig. 5. Seven Two-Spindle Shapers, Motor Driven Through 
Special Countershaft by 5 H.P. Induction Motors 



Fig. 6. Special Countershaft Device with Motor Base 

and Belt Tighteners Used for Driving Two-Spindle 

Shapers shown in Fig. 5 

the size, weight and cost of motors of a given 
horse-power are greatly reduced as compared 
with the same capacity in motors of lower 
speed. 

The accompanying illustrations show some 
very successful adaptations of high speed 
motors of small and medium size to wood 
wi irking machinery, and indicate the results 
which may be obtained by considering each 
unit in a wood working plant as a separate 
problem, to be worked out with the idea of 
obtaining the highest possible efficiency for 
each manufacturing operation. 

These machines are installed in the plant of 
Hey wood Brothers & Wakefield Company, 
at Gardner, Mass.. which is the largest chair 
factory in the world. This factory has been 
partially equipped with motor drive for a 
number of years, during which time the 
electrical outfit has been constantly added to, 
as its superiority to the previously existing 
drive was demonstrated. 

The plant is equipped with a 600 volt, 
three-phase, (ill cycle, engine driven gener 
ator, and at the present time 107 motors are 
installed, about 80 per cent, of these being of 
General Electric manufacture. The equip- 
menl includes examples of bell connected 
group drive, and belt connected and direct 
connected individual drive. There are also 
some high speed motors direct coupled to 
overhead and floor shafting, from which small 
groups of machines, practically in continuous 
operation, are driven. 



254 



GENERAL ELECTRIC REVIEW 



Many of the wood working machines in 
this plant are of original design, and most of 
those illustrated herewith were either designed 
throughout or were equipped with special 




Fig. 7- 5 H.P. Induction Motor Driving Spline Cutting Machine 



features under the direct supervision of the 
Heywood Brothers & Wakefield Company's 
engineers. The motors installed in this plant 
are all of small or medium 
size, ranging in capacity 
from ' •_> h.p. to .'!"> h.p.. with 
initial speeds varying from 
")40 r.p.m. to 3600r.p.m. 

While accurate figu 
in regard to the saving 
wer which has been 
effected by the adoption of 
motor drive in this plant 
are not available, a com- 
petent estimate indii 
that the operating expense 
for a given amount of 
duction has been reduced 
by more than 30 | ! 

A careful consideration 
of the following ii 
of the direet application 
of high speed motors will 
give a comprehensive 
of the possibilities of this 

method of drive for \v 1 

working machinery: 



Fig. 1 shows a 7 ! 2 h.p. motor which drives 

two 20 inch circular saws at 1S00 r.p.m., the 
motor being mounted between the saws and 
direct coupled to the saw shafts. These saws 
are used for cutting up large 
stock, and the shafting is 
therefore relatively long. 
Both the motor and the 
saw bearings are mounted 
on a common cast iron 
bed-plate, therein" avoiding 
any tendency to distortion 
of the shaft. In addition 
to the equipment shown, 
there is another double saw 
se1 of a similar type but 
larger size, and two single 
saws, all utilizing direct 
coupled motors. 

The illustration. Fig. 2, 
suggests one of the benefits 
of individual motor drive: 
i.e., the location of aux- 
iliary machinery where it 
will be most effective in 
insuring the continuity 
of progressive operations. 
Each unit may be placed 
wherever desired and con- 
nected to the feeder wires 
without regard to the location of the rest 
of the machinery. Fig 2 shows a small 
cutting chuck for chucking H x in. chair 




Fig. 8. 7 1 2 H. 
Machine, 



P. Induction Motor Direct Connected to Driving Shaft of Frame 
and Belt Connected to a Four-Spindle Dowel Boring Machine 



HIGH SPEED MOTORS FOR WOOD WORKING MACHINERY 




Fig 9. 1 HP Induction Motor Driving Six-Wheel Grinding Set 



spindles, mounted on the shaft of a 3 4 h.p. 
motor which operates at 3600 r.p.m.; while 




Fig 10. 



3 H.P. Induction Motor Direct Connected to 
Driving Shaft of Jig Saw 



Fig. 3 shows a circular saw, mounted on the 
shaft of a 1 h.p. motor and used for cutting 
dowels, also operating at 3600 r.p.m. 

An example of the special machines designed 
and built by the wood working company's 
engineers is shown in Fig. 4. This consists of 
a special six-spindle automatic dowel boring 
machine with a ."> h.p., 1800 r.p.m. motor 
direct connected to the driving shaft, which is 
equipped with a broad pulley from which belts 
are run to the small driving pulleys for the 
individual drills. The proper spacing of the 
six drills, which are located in a horizontal 
row at the top of the machine, is effected 
through universal joints. 

For shaping and moulding chair scat 
frames, ten two-spindle vertical shaft shapers 
are used, each double shaper being driven by a 
5 h.p., 1800 r.p.m. motor, and provided with 
a specially designed countershaft device in 
which the motor and the driving pulleys arc 
mounted on a common cast iron bed-plate. 
These driving pulleys are dired coupled to 
the motor shaft, the coupling and pulley 
being made in halves, thus insuring a 
simple, compact and strong driving mechan- 
ism. A group of seven of these ihaper is 
shown in Pig. 5, while the motor driven 
countershaft is shown separately in Fig. 6. 

That this factory has an enormous output 
is indicated by the fact that it has facilities 
for the product ion of 6000 chair ! of one type 
per day. For cane seated chairs a very large 
number of splines are required, and as the 
ordinary machine for this work cuts only one 
spline at a time, il was decided to increase the 
production of tin i detail part by constructing 



256 



GENERAL ELECTRIC REVIEW 



the machine shown in Fig. 7, which is driven 
by a 5 h.p., 1800 r.p.m. motor, and cu1 
splines in one operation. 




Fig. 11. 3 HP. Induction Motor mounted on Head Stock of Back Knife Gauge Lathe 

An instance of two interconnected machines 
involving two consecutive manufacturing 
operations and driven by a single motor is 
shown in Fig. 8. This set consists of a frame 
cutting machine and a 
four-spindle dowel boring 
machine; the former being 

utilized for cutting w 1 

for sea' frames to 
proper size and angle, and 
iter for boring the 
Eor the dowel A 7 1 ■> 
h.p., 1800 r.p.m. 
dired cted to 

driving shaft 6f the framing 
machine, which is in turn 
belt connected to that of 
the dowel boring machine. 

For grinding tools a com- 
pact grinding set arranged 
for holding six wheels and 
direct driven by a 1 h.p. 
motor at L800 r.p.m. is 
shown in Fig. 9, while Fig. 
10 shows an auxiliary de- 
vice consisting of a small 
\ driven by a ;; i h.p., 
1200 r.p.m. motor, direct 
connected to the crank 
shaft. There is a similar 



jig saw installed in the plant and equipped 
with a small self-contained centrifugal blower, 
which is also operated by the driving motor, 
thereby rendering this par- 
ticular unit independent 
of the air exhaust system 
of the factory and avoiding 
the expense of running an 
air conduit to the machine. 

The light weight of the 
high speed induction motor 
makes it possible, in many 
cases, to mount the motor 
directly on the machine 
when there is no driving 
shaft to which it may be 
coupled. An example of 
this is shown in Fig 11, 
which illustrates a baek- 
knife lathe used for shaping 
chair spindles and having 
a 3 h.p.. 3600 r.p.m. motor 
mounted on the headstock. 

Tin co ess and 

strength of the mounting 
which has been adopted as 
a standard for motor driven 

circular saws is well illustrated in Fig. 12. 

which shows a 1 h.p.. 3600 r.p.m. motor direct 

connected to two 1 2 in. circular cross cut saws. 

used for trimming seat frames. The general 




Fig. 13. 10 H.P. Induction Motor Driving Double End Tenoning Machine 



HIGH SPEED MOTORS FOR Wool) WORKING MACHINERY 
LIST OF MOTORS 



257 





No. Motors 

1 
1 
1 


H.P. 

.7.") 
3 

1 


R.P.M. 


Ni 


Motors 


H.P. 


R.P.M. 




< 

a 

3 





3600 
3600 
3600 




2 

1 
1 


.75 

1 
2 


1200 
1800 
3600 












Q 

a 

3 

u 




3 


3 


3600 






1 

3 


3 
."> 
5 


1 81 II 1 
1200 

l 81 H i 


1 

2 
1 
li 
1 

2 
2 
1 


4 
7> 
7, 


900 

1 SI II 1 

3600 

7 I'll 

Ml III 

1800 
900 
600 




Da 

c 

3 



3 
2 
2 

3 

2 

3 


7..") 
10 
1(1 
15 
l'ii 
20 


1800 

'. 

1200 
1200 

900 

1200 




7.7, 
7.7, 
10 

25 



















1 

1 
4 
■2 


."> 
10 
15 


570 
1730 

1 1 17, 

1 145 




1 
1 

2 
1 

13 

1 


1 
2 


3600 

1S00 

1800 

1 L'l II 1 

1SOO 

'.10(1 






3 

1 


20 
30 


1 1 51 1 
1 1 51 1 


u 

a 

3 


7, 
7,.7, 












O 


1 


7..i 


1 L'l III 




u 


3 

1 
2 

1 
1 
2 


5 

7.7, 
111 
15 
20 
25 


1 81 II i 
1800 
1200 
1200 
900 
1200 


6 

2 

1 
1 
1 
1 


3 

7.7, 
10 
17, 
•> 


1 SI II 1 

1730 
1 1 47, 

1117 
1 14.5 
3 Hi'i 




3 


1 


3 


1730 















1 
1 
1 
I 


10 
15 
20 
25 


1 147, 

1 1 17, 

117,0 

870 














1 


» ..» 


1200 













Group A. Operating tool directly connected to rotor shaft; as for example, a saw or chuck on the extended 

end of the rotor shaft. 
Group B. Shaft ilri iiig a group of machines belted to the shaft of the motor. 
Group C. Shaft driving a group of machines coupled to the shaft of the motor. 
Group D. Driving shaft of the machine direct coupled to the shaft of the motor. 
Group E. Driving shaft of the machine be'tcd to the shaft of the motor. 




Fig. 1.. 1 H.P. Induction Motor Direct Coupled to 
Two 12 in. Cross Cut Trim Saws 



258 



GENERAL ELECTRIC REVIEW 



arrangement of the saws and motors in this 
instance is similar to that in the installation 




nected to the driving shaft of a four-sided 

moulder, as shown in Fig. 14. 

Six rip band saws are used 
for cutting stock, all of them 
being provided with direct 
motor drive. One of these 
saws, a 42 in. Xo. 1, is shown 
in Fig. 15 and is direct con- 
nected to a 7 1 o h.p., 720r.p.m. 
motor with belt connection 
fr< mi the driving shaft to the 
\< •■•I mechanism. 



10 H.P. Induction Motor Direct Connected to Driving S 



shown in Fig. 1. The convenience of a com- 
I set mounted on a rigid bed-plate will 
be readily appreciated by those who have 
had to line up machinery of this character 
with motor shafting when installing motors 
and saws provided with separate bases. 

In addition to the set illustrated, there are 
two .", h.p. sets and one 5 h.p. set. the latter 
being used for cutting up stock for the gauge 
lathes. All of these saws operate at 3600 
r.p.m. 

Intheabo cription,we have considered 

only those motors having speeds of L200, 
L800 and :;*">< 1 r.p.m. There are, ill addition 
to tl ; examples of direct drive 

utilizing mo omewhat larger capacity 

and lower speed. These are considered below. 

A centrifugal blower for supplying the 
exhaust system of the factory employs a 25 
h.p., 600 r.p.m. motor for driving, the com- 
plete set being mounted on a platform 

pended from the ceiling beams, thereby 
rendering the spi ath the set available 

for tora 

In Fig. 13 a double end t< used 

■ cipally for the manufactun of school 
furniture, is shown. This machine cuts 
stock to length, and makes groove and tongue, 
tenon and special joints. It is driven by a 
lit h.p. motor operating at '.Hid r.p.m., the 
motor being securely mounted on a flat iron 

' plate having sufficient surface to .o 
disturbance of the shaft alignment. A motor 
of similar capacity and speed is direct co 



The applications above de- 
scribed illustrate some of the 
unusual features of the Hey- 
wood Brothers & Wakefield 
Co.'s installation, which are 
due to the initiative of their 
engineers; the extent to which 
motor drive has been adopted 
in this factory being graphic- 
ally shown by the tabulation 
on page 2-">7, which gives the 
capacity and speed of all the motors in service 
and the methods of connection used. 



Sided Moulder 




Fig 15. 7 12 HP Induction Motor Direct Connected to 
Driving Shaft of 42 in No. 1 Self Feed Band Rip Saw 



259 



COMMERCIAL ELECTRICAL TESTING 

Part VIII 
By E. F. Collins 



INDUCTION MOTORS 

The tost usually made upon induction 
motors for checking guarantees and deter- 
mining characteristics for engineering 
information arc given under the following 
headings. Wherever these tests differ from 
those employed for other alternating current 
motors they are described in detail. 

The preliminary tests made on induction 
motors include the measuring of the air gap, 
bearing and end play, slip and resistance, ae 
well as the tests for starting, running light, 
excitation and static impedance. 

Special measuring scales are used for 
taking induction motor air gap and consider- 
able care should be exercised in making this 
measurement both with the rotor in a given 
position and in different positions. 

Bearing play is taken by measuring the 
gap at the top, bottom and on each side. 
With the rotor in the same relative position 
to the stator, that is, without turning the 
rotor, the motor is turned over in all four 
positions of the quadrant and the same 
measurements of air gap taken. Any defects 
in the bearings which will affect the air gap 
of the machine are thus disclosed. 

A starting test on Form K motors is made 
by switching the machine onto the line at a 
low voltage and then increasing the voltage 
until the motor starts, the current and 
voltage at this point being recorded. The 
starting current should not exceed 200 per 

it. normal current. This test is occasion- 
ally made with a compensator. 

With all the internal resistance in the rotor 
circuit, full line voltage ihould !»• impressed 
on Form L motors and the starting current 
recorded. This current should not exceed 
normal current. 

Form M motors are started at full line 
Voltage with all the external resistance in the 
rotor circuit, and the starting current is 
recorded, which should not exceed normal 
value. Sometimes the collector rings on 
Form M motor-, are horl circuited and the 
te i made a1 n duced voltage, as in 
t lie ease of Form K motor; 

Slip is usually measured a1 lull load and 
running lighl l>v means of the slip indicati r. 
During this test, constant speed must be held 



on the driving alternator, and constant vol- 
tage on the motor. 

To take slip by the lamp method, an are 
lamp is connected in the circuit from which 
the motor is running. On the end of the 
motor shall a disk is placed which has as 
manv white and black sector:-, as there are 




Fig. 37. Slip Disk 

poles in the motor. (See fig. :!7. which is 
used for a six-pole motor.) As the lamp is 
running from an alternating current source, 
the current wave passes through zero twice 
in each complete cycle. At the zero instant, 
the light given out by the lamp is a minimum. 

Consider a six-pole (ill cycle motor running 
at ll'OO r.p.m., that is to say, at I'll revolutions 
per second; then 20X6=120 black sectors 
passing a stationary point on the circum- 
ference of the disk in one second. As the 
frequency is (Hi, the number of maximum 
illuminations will he L20. At each maximum 
illumination, therefore, the black strips will 
always occupy the same positions. 1 [owe^ er, 
the slip which always occurs in an induction 
motor will cause the black strip to lag by 
a small angle behind the position occupied at 
the previous illumination. These successive 
differences in position appear as a 
rotating backwards, which can be foil 
le the eye. The slip, that is, the difference 
ie1 " een the actual speed and the synchronous 
speed of the motor per minute, can thus he 
counted. 

The resistance of the stator should he 
measured Ci >ld and In il . 

Running light is taken by applying normal 
\ oltage to i he itator and reading the amperes 
input to ill,, up,!, ,i- Stal ic impedam i i 
taken by blocking the rotor and applying 



260 



GENERAL ELECTRIC REVIEW 



such a voltage to the stator as will give 
about full load current, reading the current 
in each leg, together with the voltage between 
each of the legs. If the motor is of the Form 
L type, impedance is taken with the resistance 
all in and then all out, always holding the 
same voltage across the stator. This practice 
has been found to give the best results. End 
play should be tested both with and without 
voltage (in the stator, and on all motors 
particular rare should be taken to see that 
the rotor is in perfect balance. 

When cutting out the internal resistance, 
the starting switch of Form L motors should 
be watched closely for sparking or any other 
defects. The brushes must make good 
contact on the resistances in all positions and 
the switch must not work too easily, other- 
wise the resistance may be cut out too 
rapidly. 

On Form M motors, the brushes must tit 
the collector rings perfectly, as a successful 
on this type of motor depends consider- 
ably on a good fit. The voltage ratio should 
be taken cm Form M motors by impressing 
normal voltage on the stator and measuring 
the voltage between the rings of the rotor on 
ii circuit. Volts and amperes stator. and 
volts between rotor rings should be read and 
r ci irded. 

Two in a motor can be obtained by 

changing the connections on the stator by 
means of a switch and connection board. 
these changes altering the number of effective 
pole-. Tin rotor must have the correct 
number and ratio of slots in the stator and 
rotor, otherwise dead points may occur at 
certain starting positions, or again the motor 
may operate at subsynchronous speed-. 
These machines are usually run at the lower 
speed during 1 1 

Excitation 

The tests for excitation and impedance are 
important, and the following precautions 
must be observed in all cases. The calcu- 
lation of the characteristic curves of induction 
motors depends entirely on test results, and 
.it care must therefore be taken to obtain 
accurate measurements. 

The motor should be located so that all the 
conditions affecting its operation during test 
remain unchanged throughout the run. A 
solid foundation is necessary to prevent 
vibration at full speed, ami the table must 
not be near any source of stray field. The 
driving alternator should be at least :l ( the 
kw. capacity of the motor. The transformers 



and other apparatus must be connected so 
that the alternator will work under normal 
conditions, since satisfactory wattmeter read- 
ings cannot be obtained if the alternator is 
run too low on the saturation curve. Trans- 
formers, when used, must be well balanced 
and not forced beyond their voltage range, 
otherwise unsatisfactory results may be 
obtained. 

The table must be adapted for wattmeters 
by providing a special wattmeter switch 
connected on two of the three phases, as 
shown in Fig. 38. A and B are the terminals 
for the current leads to the wattmeters, X 
and Z being the short circuiting switches. 
Calling the phases 1-2 3, then phase 1 is on 
the current coil of wattmeter R, connected 
at A, and the pressure coil is connected across 
1 and 2. Likewise with the other meter S. 
the current coil of which is on phase 3 at B. 
with its pressure coil between 2 and 3. If the 
voltage is too high for direct use on watt- 
meters, multipliers (non-inductive coils of 
known resistance) or potential transformers 
must be connected between the meter and 
the volt lines at the table. 

On motors of less than 20 h.p. the lines"jt0 
the primaries of the potential transformers 
must be attached to the generator side of the 
lines coming to the top of the dynamoi 



L M 




Fig. 38. Wattmeter Connections for Excitation 

board. If placed on the motor side of top of 
the board, or on the motor terminal block, the 
excitation current of the potential transformer 

through the wattmeters. Alti 
this current is small, with a small motor it 
may be an appreciable percentage of the 
excitation current. Hence an error is caused 



CI IMMERCIA] 



JLECTRICAL TESTING 



26] 



and an abrupt break made in the excitation 
curves every time the ratio of the potential 
transformer is changed. On large motors 
the excitation current of the potential 

transformer is so small in comparison with 
the motor current that the incidental errors 
are negligible. The above .Iocs not apply 
to multipliers because they are non-inductive. 

On large motors the volt leads should 
always be attached at the terminal block in 
order to eliminate the line drop in switches 
and leads from the table to the motor. The 
current leads to the wattmeters should lie 
twisted together throughout their length and 
come direct from the terminal to the meter 
without loops or sharp turns. All connections 
must be kept tight and clean. 

The air gap should be taken before the test 
is started. On voltages above 500 volts all 
instruments must have any static charge 
thereon discharged and a small fuse connected 
between the current terminal and the nearest 
volt terminal of the wattmeter. Do not 
ground the secondaries of the transformer. 

As soon as the machine is wired and ready 
to start, the switches on the dynamometer 
board should be closed. (Always see that the 
wattmeter switches are closed whenever a 
change in the field current is made.) The 
exciter field switch is then closed and the 
voltage brought up slowly until the motor 
starts and reaches normal speed. The 
machine should then be inspected to see 
that it is operating normally and the amperes 
and volts in the different phases read and any 
unbalancing corrected or its cause discovered. 

The end play of the motor should be tested 
next, since the rotor must always run centrally 
in the frame. A slight pressure against one 
side will change the friction watts and give an 
incorrect value to the core loss. Small motors 
should be run about one hour and a half and 
large ones two hours and a half or more, to 
obtain constant friction before starting tests. 
If the wattmeter needle goe off the scale in a 
negative direction when connected in circuit, 
the current leads on tin currenl terminals 
should be interchanged. On a two-phase 
circuit, with a machine under load, both 
wattmeters should read positive. 

For running light readings on a three-phase 
machine the sign of the meter musl be 
determined, ince our read i negal ive on t he 
upper pari of the curve. With both meters 
reading positive, one of the phases containing 
tin' current coil of the \v;i meter should be 
opened and the other meter observed. If the 



needle drops off the scale below zero the metei 
reads negatively. If the needle drops to 
some value above zero the reading is positive. 
This process must be repeated for determining 
the readings of the other wattmeter. 

The alternator speed must be held constant 
during the test and about bill per 
normal volts used for the first reading; volts 
amperes, watts and speed of generator and 
motor being read and recorded. The volts 
should then be decreased in steps so as to 
obtain about 2tl '2~> points on the curve, 
down to 10 or 15 per cent, of normal volts. 
Here the conditions are no longer stable. 
The meter with the negative sign will read 
less than the other, and its readings will fall 
off more rapidly, becoming less and less until 
zero is reached and its sign changes. When 
it becomes positive, the current leads must 1 le 
interchanged. 

After the volts have been reduced from the 
starting point of curve to normal, three 
single-phase wattmeter readings, one above, 
one below and one at normal voltage, should 
be taken on the two legs to check the results. 
Check readings should also be taken with a 
different voltmeter and ammeter. 

The single-phase excitation amperes are 
theoretically 1.7:5 times the three-phase and 
twice the two-phase values; that is, the kv-a. 
has equal values for the motor, whether 
single-phase or polyphase. Practically, the 
single-phase amperes are from 1.6 to 1.7 
limes the three-phase, instead of 1.73 times. 
The same ratio holds for quarter-phase. 
The watts excitation is the same for polyphase 
or single-phase, so far as core loss is con- 
cerned. The increase in watts single-phase 
over the watts polyphase is equal to the 
polyphase C 2 R. For instance, if the three- 
phase excitation requires 101 ill watts and the 
C-R three-phase is 100 watts, the single-phase 
excitation will be 1 100 watts. 

Before shutting down, a curve should be 
plotted with volts as abscissa 1 and the 
algebraic sum of the watts as ordinates. 

Wattmeter work is somewhat uncertain. 
and accurate results can only be obtained 
miller good conditions. An endless bell on the 
driving alternator is necessary, a laced belt 
making the wattmeter needle swing with a 
steady beat corresponding to the striking of 
lacing on the generator pulley. Any bell 
running near the table must have their 
Static charges drawn oil by a grounded wire 
and the cases of all t ran Eormi I should becon 
,1 togel her and grounded. Wal I meter. 



262 



GENERAL ELECTRIC REVIEW 



must be carefully handled on high voltages, 
since all three phases of the alternator are 
connected on the table and contact between 

TABLE XVI— Excitation on a 100 H.P., 2080 V., 
6-Pole, 60 Cycle, 3-Phase Induction Motor 



Volts 



2510 

2370 

2175 

2105 

2075 

2020 

1830 

1610 

14-40 

2160 

2070 

21 ii ii i 

2070 

2200 

2235 

1366 

1 1 85 

988 

816 

585 

185 

292 

244 

i 



Amps. 


Watts 
+ 


1 1 .5 


18300 


1(1.4 


15500 


9.5 


li". 


9.2 


12090 


8.8 


1147(1 


8.6 


10870 


i .i 


9060 



6.76 
6 03 
1 :.. 1 
14.6 
14.2 
1 1.6 
15.85 
15.9 
5.78 
5.08 
4.3 
3.75 
; 35 
3.25 
3.9 
L85 
5.8 



6950 
5740 
5 150 
4750 
4550 



.-.440 
4390 
3185 
2550 
1670 
1370 
1200 
121(1 
974 






12150 
9900 

81 ii ii i 
7380 
6920 
6370 
5060 
3450 
2670 



1950 

:,1 til 
5540 
2310 
1540 

c.s.-, 
ITS 
+380 
530 
644 
673 
.-,iiu 



Total 

Watts 



6150 

5600 
4900 

471(1 
1550 
4.")iKl 
4000 
3500 
3070 



3130 
2851 1 
2500 
2372 

207.(1 
1900 
1.X44 
L883 

1474 



two of the instruments short circuits one of 
the phases. 

The two important points on an excitation 
curve are the watts at normal voltage and 
friction watts. These points determine the 
percentage core loss for the motor. Several 
readings, only a few volts apart, should be 
taken on each side of normal voltage and the 
volts and amperes in the different phases at 
two or three other points in the curve should 
be carefully read and recorded as a check on 
the balance of the motor. As the lowest point 
of the curve, or friction reading is approached, 
main- readings should be taken. This portion 
is the most difficult part of the curve to 
locate, especially in the cue of large motors, 
as in many instances "hunting" begins at a 
low voltage. A reading taken when the motor 
is accelerating is of greater value than the 
steady reading. 

Hunting usually makes the meter needle 
swing with a slow beat, the range of the heat 
Varying with the size of motor and degree of 
hunting. Had cases of hunting arc not 
numerous and reliable readings can generally 
be secured between beats. To test success- 
fully, the speed of the driving generator must 



be kept constant and no reading taken until 
the speed is properly adjusted. The tachom- 
eter used must be carefully checked. 

The excitation tests on all forms of induc- 
tion motors are the same. 

The Form M motor is provided with 
collector rings for the external resistance. 
These must be short circuited at the brush- 
holder terminal and the brushes carefully 
sandpapered until they fit the rings accuratelv. 

Calculation of Excitation Test on Induction Motors 

All readings must be corrected for the 
instrument constants and ratios used. Special 
care should be taken to use the proper signs 
for the wattmeter readings. Table XVI 
shows the form used in calculating an exci- 
tation test, and Fig. 39 the method of 
plotting it. The friction and windage watts 



s 

I 

13 

14 
13 
IZ 
II 
10 
9 
8 
7 
6 
5 
4 
3 
Z 
I 



■ 


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h 


i w- 


A 


*f- 


it x ^ 


r 




it t 


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-t/ 






S -+--f- -+-7l- 


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l-t^ ^T T3I-t 


^11 ! ! rcV 


T ' II _tlt"^z _t 


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■ -p- ^-' 


^ — -■" 4 "" 


*" ^. . —»— ""*"" 


/ , .!ii 



'0 400" 800 /200 /eOO 2000 Z400 2600 
Vb/tS 

Fig. 39. Excitation Curve on a 100 HP., 2080 Volt, 
1200 R.P.M., 60 Cycle. 3-Phase Induction Motor 

are obtained from the excitation curve by 
producing the watt curve to zero volts. 

Impedance 

The Form K motor has a symmetrical 
bar winding in the rotor and therefore the 
impedance is the same for any position of 
the stator relative to the rotor. 

In Forms I,. M and P, which have wound 
rotors, a position curve is first taken. 



COMMERCIAL ELECTRICAL TESTING 



263 



Two-thirds of the distance between two con- 
secutive poles on a three-phase motor and 
one-half that distance on a quarter-phase 
motor arc marked off on the bearing bracket, 
this space being divided into about eight 
parts. A pointer should be attached to the 
motor shaft or pulley so that its outer end 
will pass over the division marks; it is then 
set on mark 1 and the rotor blocked s. > that 
it cannot move from that position. The 
switches arc next closed and the impressed 
voltage increased gradually until about nor- 
mal current is obtained. Volts and amperes 
should be read and recorded on all three 
phases to make sure that no unbalancing 
occurs. Holding the same volts as for 
position 1, the pointer is moved to mark 2, 
and the amperes read; this procedure being 
repeated on each of the succeeding marks and 
a curve plotted, giving amperes and pointer 
position. The motor is then blocked in the 
position which gives an average value of the 
current. Form K induction motors are 
blocked in any position. 

The current is then increased until 150 
per cent, normal current is obtained, and the 
amperes, volts and watts are read. The sign 
of the wattmeter must be determined in the 
same way as at the beginning of the exci- 
tation test. About six or eight readings should 
be taken between zero and 150 per cent, 
normal current, but the current should not be 
held on the motor longer than necessary to 
secure a reading. After each reading the 
exciter field should be opened, until ready for 
the next reading, otherwise the motor will get 
too hot. As soon as the readings are taken, 

TABLE XVII — Impedance on a 100 H.P., 2880 V., 
6-Pole, 60 Cycle, 3-Phase Induction Motor 



Volts 


Amps. 


Watts 

+ 


14f> 


11.!) 


1230 


188 


1."] 


1870 


220 


IS 


2825 


263 


21.5 


41 Kill 


301 


24 


5260 


:::,.-, 


28.5 


, 2.").") 


384 


30.7 


8360 


4111 


33 


9450 


455 


36 


1 L680 


297 


20.6 


— 


271' 


19.1 


— 


322 


..., ., 


— 


27.'i 


19 


1 2.").". 


297 


20.5 


1 .",1 II 1 


.S22 


22.2 


1720 



Watts 



Total 
Watts 



447, 


785 


Ill ill 


1210 


1 11X11 


17 1."! 


1 is;, 


2575 


L930 


3330 


2845 


4410 


3190 


5170 


;i7io 


5740 


1 150 


7230 


1460 




1 190 




1680 





curves should be plotted with volt 
abscissae, and amperes and the algebraic sum 
of the watts as ordinates. The ampere curve 
should be a straight line, though sometimes 
the top portion curves upward very slightly. 



if —r- —r~ 










izzlz 




: tizzz 




i 




'- i zt 




t^ztXT x 




ii ill 




/' 




- " -jXIt 




+ FIT 




±^C±± 




./ 


fc 


zjatt ^ ,_ 


< 


i&_n_xx 


^ 


v/ I 


sS 


V XXIH 


1 


-+-x?ttix-^xc 


^ 


XXXX 


- 


i_ i_u 6 c£ x 


&° 3 


' jfl"* 1 


is 


/ vjf 


1 


f s \s 




~17L.&.AL~^± 


\20 Z j> 


>i 


r v Kr 


/ 


J/m l 


,n / ,2/ 


~- <&■ X 


IO / 7 <-? 


*>■ 


s s 




*+' i- 




ot? ±. 


: x 



/oo 



200 300 



400 500 



Fig. 40. Impedance Curve on a 100 HP.. 2080 Volt. 
1200 R.P.M., 60 Cycle. 3-Phase Induction Motor 

Single-phase check readings should be 
taken, one above, one below and one at 
normal amperes, on the two phases containing 
wattmeters. 

The single-phase impedance current should 
be S6.5 per cent, of the three-phase (line) 
values. The single-phase impedance watts 
should be approximately half of the three- 
phase watts. In a quarter-phase motor 
single-phase impedance is the impedance of 
one of the two phases. 

On Form M motors, when taking impedance, 
the collector rings should be short circuited 
either by metal brushes or by metal strips, 
as the contact resistance varies with carbon 
brushes. The ratios between the primary 
and secondary voltage should be taken with 
the secondary open circuited. 

Calculation of Impedance Test on Induction Motors 

Table XYII shows the form used in 
calculating an impedance test, and Fig. 40 

the method of plol ting it. 

/ o bt Conlt 



264 



GENERAL ELECTRIC REVIEW 



HYPERBOLIC FUNCTIONS AND THEIR APPLICATION 
TO TRANSMISSION LINE PROBLEMS 

Part III 

By W. E. Miller 



Transmission Line Characteristic Curves 

To illustrate how the volts, amperes and 
power factors vary along a transmission line, 
the electrical conditions being determined at 
the receiving end, various curves have been 
plotted for a line 41 Ml miles long operating at 
60 cycles and using three No. 0000 hard 
drawn stranded cupper wires triangularly 
spaced 111 ft. apart. In all cases the volts 
received nned constant at 60,000 volts 

between wire and neutral, i.e., 104,000 volts 
between wires. 

Fig. II) shows the variation of the volts 
along the line with unity power factor at the 



slightly greater than that at the generator 
end. When the received current is 17 u 
amperes, the generator current has the same 
value. 

The volts at no load. Fig. 10, rise from the 
generator towards the receiving end. With a 
current of 102 amperes receiving end at unity 
power factor, the generator and received 
volts become equal, a maximum voltage 
occuring about halfway along the line. When 
the received current is greater than 102 
amperes, the voltage drops along the line 
from the generator towards the receiving 
end. 




v 30 

Genera /or End 



ZOO 
Mi/es 



MO 4W 

Receiving End 



Fig. 



10. Variation of Volts along 400 Mile Three-Phase Line. Using Three No. 0000 B.&S. Wires 10 ft. apart. 
Operating at 60 Cycles, 104.000 Volts between Wires at Receiving End. Unity Power Factor at 
Receiving End. and conditions as stated on curves 



receiving end for the following cases: 3600 kw, 

and 7200 kw. delivered per phase — equal 

current values at the generating and receiving 

ends- unity power factor maintained at both 

ends. Fig. 1 1 shows how the current varied 

the line in the above eases. 

It should be noted that when 3600 kw. is 

delivered the current at the generating end is 

more than double that at the receiving end; 

when, however, the power delivered is 

doubled, the generator current is only 

increased I'll amperes. To maintain unity 

er factor at both ends, the current at the 

iving end must be 107 amperes, which is 

ERRAl 1 /.i(... \///. pat* 11 pltmcut. 

Equation numbers on pag< «.'■/ rttiii 

\nd SH in />/./ 



Fig. 12 shows the variation of volts and 
current along the same line when 12(1 amperes 
are delivered at .90 leading and lagging power 
factors respectively. With a leading power 
factor at the receiving end, the current at the 
generator end is very much larger than that 
a; the receiving end, whereas the volts rise 
slightly towards the receiving end. Thus a 
leading power factor at the receiving end 
means a high transmission loss along the line. 
(In the other hand, when the power factor is 
.'.in lagging at the receiving end. the current is 
nearly equal at both ends, being minimum 
half way, and the transmission efficiency is 
nearly maximum. The volts in this ease drop 
slightly from the generating end towards the 
receiving end. 



LONG DISTANT 



TRANSMISSION LINE PROBLEMS 



26 



Curves C and A, Fig. 13, illustrate t he varia- 
tion of the power factor along the line for the 
two eases just mentioned. When the power 
factor is .!)() leading a1 the receiving end. it has 



a considerable variation occurs. The trans- 
mission efficiency in this case is 85 percent., 
whereas, with the power factor leading at the 
receiving end. the efficiency is only 7 I per cenl .. 











































































































1 












































\_J/mYi/ Power Factor at Both Ends 



























180 






















Fauat Current at doth ' Endsitnit, Power Factor ffeeemnqF^ 




































































160 




































































































































140 












#0A 


'fizza*,^. 






























































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IPO 






























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eeiyinqFnd 




















(9 












-&i. 


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§ 100 












ht^ 


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rr^ 






























% 80 






















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P 




























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S. 60 


































£&/ 


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4 






































■4V 


























40 




































































































































20 




































































































































n 

































































50 100 

Generator End 



130 



ZOO 
Miles 



250 



J00 



J50 400 

HeceivinQ End 



Fig. 11. Variation of Current along 400 Mile Three-Phase Line. Using Three No. 0000 Wires 10 ft. apart. 
Operating at 60 Cycles. 104.000 Volts between Wires at Receiving End. Unity Power Factor 
at Receiving End, and conditions as stated on curves 



minimum value about '2ND miles from the 
generating end, rising to .94 leading at the 
latter end. Thus, only a small variation of 



the same kw. being delivered in both cases. 

Curve B, Fig. 13, shows the variation of 
power factor when 7200 kw. at unity power 



vrEcctor LdqqwfZwmw, 




'gffecemnqf?,, 



ill I I 




ifc^% A Ur^^^^^^r 



50 

Generator End 



150 



200 
Mites 



250 



500 



LA4.0000 



350 400 

ffeceivinqEnd 



Fig. 12. Variation of Amperes and Volts along 400 Mile Three Phase Line. Using Three No 0000 B &S Wires 

10 ft. apart. Operating at 60 Cycles. 104,000 Volts between Wires at Receiving End. Power Factor 

Receiving End .90 Leading and Lagging 



power fad or occurs alcnig the line. When, how- 
ever, the power factor is 90 lagging at the 
receiving end, i1 is .90 leading al the generator 
end and unity halfway along the line, thai is, 



factor arc delivered and Curve I) slum the 
variation of power factor when 3600 kw. are 
delivered. In the latter case, the power • 
is only .68 leading a1 the generator end. 



266 



GENERAL ELECTRIC REVIEW 



Curve E shows the variation of power factor 
with no load at the receiving end. the line 



Curve C, Fig. 14, shows how the current 
varies with the power factor at the receiving 



^.90 






— - 






































If 




. 


















































































.90 









































-£>- 






-^ 








— i 










































£ 










*■ 
























.80 


































































































































































n 




































.70 




































































% M 




































































— i — ' 




























































£ -so 


—\ — ■ 

































































































































*\ M 




































































































































1 30 


































































































































.20 






































































































































.10 






































































■ 
















£ 




















































































































L 


7 


iei 


at 


5 



fa 


</ 




IL 









It 


w 






2L 
M 




s 




250 






100 






350 400 

ReceivinqEnd 



Fig 13. Variation of Power Factor along 400 Mile Three-Phase Line. Using Three No. 0000 B.fltS. Wires 

10 ft. apart. Operating at 60 Cycles, 104.000 Volts between Wires at Receiving End. Curve A, 

120 Amperes Delivered at .90 Power Factor Lagging. Curve C at .90 Power Factor Leading. 

Curve B. 7,200 Kw. Delivered and Curve D. 3.600 Kw Delivered at Unity Power 

Factor Receiving End. Curve E No Load Delivered 



loss being •">l(i kw. per phase and the power 
factor .1 15 leading at the generator end. 

Transmission Efficiency 

It is of some interest to discover what 
power factor should be maintained at the 
receiving end for a given voltage and load 
delivered to obtain maximum transmission 
efficiency. Unlike transmission by direct 
current, the efficiency does not necessarily 
increase with decrease of load delivered. 
hi fact, for every transmission line, there is 
one particular load delivered for which the 
transmission efficiency is an absolute max- 
imum for that line. This load in the case of 
lon^' lines may represent a considerable 
amount of power; the load current at receiving 
end must have a fairly large value at a small 
lagging power factor to give equal current 
at both ends. 

Maximum efficiency for a given load deliv- 
ered occurs when the currents at each end 
arc equal, this condition being always obtain- 
able by varying the power factor at the 
■ i i eiving end. 



end for 7200 kw. delivered; this curve being, 
of course, immediately obtained from the 
relation between k.v.a. and kw. delivered, 
the voltage at the receiving end being held 



/60 















































































C 


















\ 




4 




























\ 




^ 


** 
























. 




V 








































O 


«== 














































































































_£ 










3 


























1 







/40 



^■/zo 

\ 

2 /oo 

X 

\ so 



eo 

/.0 .30 .80 .70 .60 

fbtrer factors Lagg/ng /fece/v/'/tg if/*/ 

Fig. 14. Curve C Gives Values of Received Current for 
Various Power Factors at Receiving End. and Curve D 
Values of the Generated Current for the Same Power 
Factors, with 7.200 Kw. Delivered. Curve F and E 
Represent Values of Received and Generated Current 
for Various Power Factors, with 3,600 Kw. Delivered. 
Three Phase Line 400 Miles Long. Using Three No. 0000 
Wires 10 ft. apart. Operating at 60 Cycles. 104.000 
Volts between Wires. Receiving End. 



LONG DISTANCE TRANSMISSION LINE PROBLEMS 



267 



constant at 60,000 volts between wire and 
neutral. Curve D is obtained by calculations 

from the transmission line equations and 
connects the generator amperes with various 
power factors at the receiving end for the 
given load and voltage delivered. The 
intersection point of Curves C and I) deter- 
mines the receiving end power factor at 
which the currents at each end become equal, 
i.e., at 128 amperes. On Fig. 1.1, curves have 
been plotted connecting volts at the generator 
end with the power factor at both the receiving 
and generator ends. These curves were 
calculated from the transmission line equa- 
tions, the conditions being 7,200 kw, delivered 
at 00,000 volts. 

The intersection point A occurs at a power 
factor .935 lagging (receiving end) (see Fig. 



Thus, to obtain maximum efficiency for 

this line when delivering 3,600 kw. per phase 
or a total of 10,800 kw., a low lagging power 
factor musl lie maintained a1 the receiving 
end, i.e., .67. With twice the delivered 
power, i.e., a total of 21,000 kw., the powei 
factor at the receiving end must be .935 
lagging and the load need only In- slightly 
inductive to obtain this value. It follows, 
therefore, that the condition for maximum 
efficiency can he obtained for fairly high 
loads along transmission lines, hut when 
light loads are in consideration, the highest 
efficiency is impracticable. 

Note on Capacity Calculations 

As it is generally easier to calculate the 
self induction between wires or between 
wire and neutral than the capacity, the 



900O0 



k 80000 





























































































































































nc.< 


ie iiver 


eo 






















































*f 


nJ 


Ti, 


























\ 
































5« 


^u^ 


































\ 
























-f- 














~* 


VL 


■ ' 


— 


Mei 


ed 


















i 


















^ 










id' 


it> 


Urn 


/J 


ffl 


























f 




















i 




-J/£ 




5* 
















| 


















i 
i 




















1 1 
























i 


















i 




















]/ 






























-t ■ 


















! 




















i 








1 






















l 
1 


















i 

i 




















i 





5; 70000 
| 

x 60000 

\ 

|" SO '000 

J,40O00 

I '■<> 

% Power Factors /j7gg//?jg /?ece/vin$ £/?d 



.90 



.80 



.70 



.60 /.O .90 .80 .70 

Power Factors leading Send/of c~r>d 

Fig. 15. Values of Volts at Sending End for Different Power Factors at Receiving and Sending Ends. 7.200 Kw. 

and 3.600 Kw. per Phase Delivered. 400 Mile Three. Phase Line. Using Three No. 0000 B.&S. Wires 10 ft. 

apart. Operating at 60 Cycles. 104.000 Volts between Wires, Receiving End 



.80. 



14), the corresponding volts at the generator 
end being 72,500 volts at a power factor .935 
leading (sec Fig. 15). Hence, the maximum 
transmission efficiency obtainable with this 
line, for 7200 kw. delivered per phase, is 

7200X1000 

72~500X128X.935 

The curves E and F have also been drawn 
for 3600 kw. per phase delivered, point B 
being the intersection of the ampere curves 
drawn for the generator and receiving ends. 
This point corresponds to 89 amperes a1 .07 
power factor lagging (receiving end), the 
generator volts being 66,500 and the power 
factor at the generator end .005 leading. 

The transmission efficiency in this case is, 
therefore, 

3600X looo 



following method for obtaining the value of 
the capacity from the value of the self 
induction is sometimes useful. It is based on 

the fact that the expression — represents 

\ LC 

(in the case of commercial transmission 
lines) the velocity of light in miles per second 
when /. is expressed in henrys per mile and 
(' in farads per mile. In using this formula /. 
should be calculated, neglecting that part of 
the self induction due to the llnx within the 



wires. Then C = 



(34) 



00, .",00 X SOX. 0)0.") 



.875, 



2.87X10 

;•■-/. /. 

Tin method was used for calculating the 

capacity between wire and neutral for 

three-phase lines when the wires lie equally 

paced in a plane, and are transposed to 

balance the phases. 

i To be ' 'ontiitued) 



26S 



GENERAL ELECTRIC REVIEW 



ELECTRICITY IN THE MINES OF THE DAVIS COAL AND COKE CO. 

By R. Xi ii Williams 
Consul hnc Engineer 



The causes which have led to the general 
adoption of electricity as a motive power in 
mining work arc mostly obvious. The only log- 
ical competitor of electricity is gravity, which 
is, of course, the cheapest power as Ion- as its 
use does not involve too much loss of time, 
or its inflexibility necessitate an expenditure 
for labor of a sum sufficiently great to offset 




Power Plant of Davis Coal and Coke Co.. West Virginia Central Junction 



aving in investment and that effected by 
the elimination of the fuel hill. Where 
conditions do no1 permit of making use of 
gravity, either horses, mules or electric 
locomotives must he employed; advanl 
being much in favor of the latter, especially 
when tlu- thinner i coal are exploited. 

The horse as a factor m coal-minim' became 
of minor importance with the advent of electric 
haulage in 1887. The mortality 
used in mining work is extremely high, while 
the first mining locomotive built in the 
United Slates, for the L\ kens Yallc 
is still hauling coal in i ervice. 

This feature is accentuated bj the necessity 
of using very small horses in mining work and 
o1 I heir working in the dark and in had air. 

The economic advantage of electric opera- 
tion becomes evident from an inspection 



of the pay roll, for with electric locomotives 
longer trips can be made at higher rati 
speed, with the result that one locomotive 
will do the work of fifteen horses on the 
average. This means the employment of one 
good man instead of fifteen boys, and the 
expenditure of $2.50 to $3.00 for power 
instead of $7.50 for feed. 

The advantages of electricity 
as a source of power in coal 
mines where the electric instal- 
lation has been properly made 
and is wisely managed are 
exemplified in the equipment 
of the Davis Coal and Coke Co.. 
which i tperates bituminous mines 
in West Virginia along the lines 
of the Western Maryland Rail- 
road Company. At the present 
lime this company owns 160,000 
acres of coal land and operates 
mines at West Virginia Central 
Junction, Elk Garden, Harrison 
Harrison being included in the 
Elk Garden district I, Henry. 
Thomas, Coketon and Weaver; 
these places being situated, in 
the order named, along the West 
Virginia C. & 1'. Division of the 
Western Maryland Railroad, 
which begins just above Pied- 
mont, W. Va.. at the junction 
of this railroad and the B, & < ». 
In the Fairmount region the company also 
owns 30,000 acre, of coal lands, which, 
however, are not being worked. 

It is interesting to follow the development 
of this company through the various sti 
of its growth and to note how systematically 
the various managements have worked 
well thought out plan of electric operation. 
While the use of electric power in the first 
place was made imperative by the nature of 
the working, its advantages in other direc- 
tions than those which compelled its adop- 
tion became apparent and led to the intro- 
i) of electricity for other purposes. 
Realizing that the distances over which it 
would be necessary to transmit electrical en- 
ergy were, in many cases, ahead) tOO great for 
t he economical use of direct current, and that 
as the operation in the mines extended all these 



ELECTRICITY JX THE MINES OF THE DAVIS COAL AND COKE CO. 



269 



distances must necessarily become greater, 
it was decided to use alternating current 
wherever possible. The greater economy of 

alternating current for lung distance trans 
mission was not, however, the only consider- 
ation which was influential in the adoption 
of this policy. The alternating current system 
is very much more flexible than any direct 
current system, and is adapted readily to any 
distance of transmission by means of the 
simple alternating current transformer. 
Furthermore, the induction motor is admir- 
alty suited fur use in coal mines, particularly 



which direct current had to he transmitted, 
it was decided to generate it at a potential of 
600 volts. The objection which might he 
raised to this high potential, due to the 
danger to men and animals, where the latter 
are still used for gathering, is more imaginary 
than real, owing to the fact that the eurrcnt 
is turned off while the shifts are changing. 
In fact, there has been no loss of human life 
from electric shocks in the company's entire 
history, and only a few instances in which 
animals have come into contact with live wires 
and were electrocuted. In these cases, the 




500 Kw., 600 Volt, Curtis Turbine Generator Set at Thomas, W. Va. 



for driving pumps and fans which run 
continuously. As it requires no brushes or 
other devices for making electrical connection 
with the secondary circuit, tin- rotor revolves 
very freely and there is no friction other than 
that of the bearings. This arrangemenl 
requires a minimum of attention and ensures 
ah olutelv no sparking. A motor of this type 
will operate for long periods of time with no 
further attention than an occasional i t . 
t i- .li of the oil gauges and air gap. 

For haulage and hoisting purposes, the 

dired current series motocwa adopted, due 

characti ri ii oi maximum torqui al 

starting. Owing to the long distano 



accident was due to the slowness of the 
drivers in getting back into the workings. 

The electrical development has hcci. con- 
sistently carried out throughout all of the 
various workings with (>(>(> volts direct current 
lor haulage and three-phase alternatinj 
rent, at a frequency of tin c\ de . for all other 
purposes, with, the exception of the lighting 
of the various mitim I For this 

puriM.se, single-phase alternating currenl is 
used, constant current tub transformers 
1 ieing employed for the li' of si reets. 

This policy of buying uniform apparatus 

for all mil tandardizing the make 

of machinery, has resulted in an almost 



270 



GENERAL ELECTRIC REVIEW 



entire absence of an electrical junk pile. It is 
a case of the pitcher going to the well till it is 
broken, and but for the advent of greatly 
improved steam motive power in the form of 
the Curtis steam turbine, there would have 
been very little noticeable depreciation in any 
of the apparatus. As it is. the increase of 




150 Kw., 600 Volt Engine Driven Direct Current Generator 



power required by the rapid developments in 
the last year or two lias made it necessary to 
ite the older reciprocating steam units in 
multiple with the steam turbines? but it is 
hoped that in a short time it will be able to 
di continu ome of the less efficient steam 
engines and use the corresponding alternating 
current generators as synchronous condensers 
to improve the power factor of the general 
system. 

The importance of the work being done by 
the induction n mine ventilation and 

pumping is so greal thai tto i orsmusl of 

lected ainnh large for the duty. 
Stinting in this respect would be poor policy, 
but naturally the result of having partially 
loaded motors continuously in 
results in a very poor power factor tor the 
whole system. The main objection to low- 
power factor in mining work is not the 
it} of providing transmission lines 
large enough to carry the excess idle current. 
but chiefh < me i if stal ion & A unit 



consisting of steam driver and electric 
generator designed to deliver an output of, 
say, 100 kilowatts at 111(1 per cent, power 
factor can only be called on for 55 kilowatts 
at 55 per cent, power factor, and not even for 
this unless the fields and armature have been 
specially designed for such operation. Even 
assuming this to be the case, 
the steam end of the unit 
would be operating at but 
little more than half load, and 
consequently with very poor 
efficiency. It is, therefore, 
desirable to bring up the 
general power factor as near 
as possible to 100 per cent. 
by means of units independ- 
ent of the generators. Rotary 
condensers, or synchronous 
motors, operating as motors, 
arc suitable for this purpose, 
whether running idle or with 
load. It is not always possi- 
ble to provide a suitable load 
for a synchronous motor in 
the interior of the mine itself, 
as this type of machine will 
not operate with the small 
amount of attention required 
li\ an induction motor, and 
is more susceptible to fluctu- 
ations in the supply of elec- 
tric energy. However, there 
is no reason why fans outside 
the mines and not too Ear from the power 
station or repair shops, where expert attention 
is available, should not be driven by syn- 
chronous motors. If the motor runs idle, the 
improvement in power factor is gained at 
the expense of an amount of energy repre- 
senting the losses in the motor. 

In the following history of the Davis 
Coal and Coke Co. and its development, the 
electrical equipment will be discussed in 
conjunction with the description of the 
various workings. 

In ISM some prospectors in the employ of 

II G. Davis & Bro. discovered the Davis 
vein of coal near Thomas, W. Va. This was 
the beginning of the present company and of 
operations at Thomas. In 1886 II. G. Davis 
& Bro. and S. I!. I.lkins formed a partnership 
for the purpose of opening the Davis coal at a 
point about a mile south of Thomas, at what 
is now known as Coketon, \V. Va. In 1887 
the first coke ovens were built and experiments 
made as to the coking qualities of the coal. 



ELECTRICITY IX THE MIXES OF Till- DAVIS COAL AND CUKE CO. 



which was found to be indeed an excellenl 
coking, steaming and smithing product. In 
1888 the Davis Coal and Coke Company was 
incorporated with an authorized capital 
stock of $250,000, which in 1893 was increased 
to $3,000,000 to enable the company to 
acquire controlling interests in several other 
mines operating on the line of 
the W. Va. Central Railway. 
From this time on, until the 
taking over of the road by the 
Goulds as the coal operating 
department of the Western 
Maryland Railroad, the develop- 
ment of the company from a 
technical point of view has 
been systematic and comprehen- 
sive. 

Taking the various operations 
in geographical rather than his- 
torical order, we will begin with 
the mines nearest to Tidewater. 
At "West Virginia Central Junc- 
tion there are four operations, 
two in what is known as the 
Bayard formation, which carries 
t he Bakerton seam of coal and 
is locally known as the "four 
foot;'' and the "three foot" 
coal, operated elsewhere as the 
upper Frceport seam. These 
mines are operated by the Gen- 
eral Electric system of rope haulage. As 
the mines are on the extreme eastern out- 
crop, the pitches are very heavy and haul- 
ages are located at the extreme end of the 
headings on the inside of the mines. Empties 
are hauled in with the rope and the loaded 
cars dropped out by gravity, dragging the 
rope behind them. The loaded cars are 
controlled by brakes on the hoisting drums, 
which arc operated bj 550 voll direel current 
irs. The Bakerton scam is at the very 
top of the Bayard formation and, since the 
north branch of the !'■ tomai river cuts the 
\ allc deep a1 this point . the above two mines 
are opened very high on the hillside and 
require inclined planes 2100 feel in length to 
reach the railroad track. Mine No. Mi is 
operated at the base of these planes, on the 
lower Kittanning seam, known locally as the 
"six (<>■•'■ This mine also requires ropi 

haulage, which is placed on the inside of the 
mine as in the case of the two mines above 
referred to, Nos. 50 and 51. The powei 
tatiort for this group is i |uipped with a 
150 lav. General Electric generator driven 



by a Buckeye engine. These three mine-. 
together with number 17 on the opposite side 
of the river in Maryland, which uses endless 
rope haulage, constitute the West Virginia 
Central Division, under the direction of 
Mr. O. Tibbets, Superintendent. 

The next group of mines, located at Elk 




Hoisting Drum Operated by Direct Current Motor 

Garden, are principally in the Pittsburg 
formation. These mines arc Xos. (i and 9 
in the Pittsburg formation; No. 10 in the 
upper Sewickly, which is known locally as gas 
coal; No. 20 in the upper Freeporl scam on a 
line with the railroad; and No. 14 four miles 
west of No. 2(1 on Abrams creek, producing i 
very high grade coal. With the exception oi 
No. 6, which has a gravity rope haulage, 
this group is not provided with mechanical 
haulage other than steam trams. Mr. Roberl 
Grant is superintendent of the Elk Garden 
district with headquarters ai Elk Garden. 
At Henry, about 8 miles cast of Tho 
is located one of t he later and, consc(|net 1 1 i ■ 
one of the more modern of the compat 
operations. The complete Bayard and Sai tg< 
formation; arc accessible from this plant, the 
upper Freeport and the lower Kil 
being in good workable condition I' i 
operate. 1 by shafts I and 2 tapping the upper 
Freeport at a depth of 250 feet and the 
lower Kittanning at 150 feet. Tipple . and 
hoisting towers are buil i I. w hile 

power house, engin housi ' ith hop 



GENERAL ELECTRIC REVIEW 



and all buildings in connection with the mine 
are of brick. The plant is equipped with 
electric haulage throughout and the coal is 
mined with compressed air punching machines. 
The power house (..mains two 24*x26*x30" 
Ingersoll air compressors, one belted 150 
kw. alternating current generator, one 




with a drift opening slightly to the dip in the 
same seam of coal. Mine No. 24 is in this 
same group, and is worked from a shaft 200 
ft. deep penetrating to the Davis seam of 
lower Kittanning. The seam is divided 
horizontally by a rock, the portion above the 
rock being 8 ft. thick and that below :; ft. 
thick. The rock serves the pur- 
pose of a pavement and. therefore, 
the coal below it is not worked to 
any extent in this mine. The coal 
is of an exceptionally good quality, 
ninning less than 1 per rent, in 
sulphur and seldom over li per cent, 
in ash, making No. 1 coke equal to 
the Connelsville. This group of 
mines is operated entirely by el 
haulage and all pumps are driver, 
by alternating current motors. 



Hoisting Drum Operated ty Direct Current Motor 

250 kw., 600 volt direct current generator 

for haulage purposes, and a synchronous 

motor direel current generator set. which 

connecting link between the two 

rating units, permitting cither one or the 

other to be shut down. This set can be oper- 

1 from either end so as to provide direct 

or alternating current. On the main roads 

of this mine the hauling is done with one 

13 ton ;ni(l ,,ne Hi toii locomotive (the latter 

of Genera] Electric manufacture), while the 

coal is gathered with two General Electric 

gathering locomotives of l ' ._, tons each. In 

portions oi the mine the coal is still gathered 

by mule haulage. Mr. W. J. Christopher is 

uperintendenl of this divi 

The next operation is at Thomas, where the 
upper Freeporl coal is mined by drift mines 
at tipple height above the railroad. No. 23 
it ine l'a been opera ted for a number of years 
and has become quite extensive in its workings ; 
it is. however, -till a good mine, producing 
li'op tons of eoal per day from a seam 8] ■_> ft. 
thick, and is free from an\ noxiou 
Mine Xo. 25 is directly opposite mine No. 23, 



The 114 coke ovens at this plant 
are served by electrically operated 
coke larries, the electrical equipment 
of which is of General Electric man- 
ufacture. The results obtained with 
these larries, which run along the top 
of thi' ovens where the heat is at 
times excessive and where the fumes 
from the ovens would be injurious to 
horses or mules, have been excellent. 
It has also been found that they are 
much quicker in operation, for the 
control is so much better that, when 
about to discharge into the oven, they car. 
be moved backward or forward an inch at 
a time. They are used either independently 
or with trailers and offer a flexibility not 
otherwise obtainable. 

The electric equipment of the larries has 
given virtually no trouble at all. On the 
other hand, as the workings in these mines 
have become more and more extensive, 
trouble lias been experienced with the 
haulage locomotives, as the length of hauls 
is very great and some steep grades arc 
necessary. The capacity of tin trolley line 
was increased by the addition of copper in 
order to reduce the drop in voltage resulting 
when heavy loads were started up at the 
working face, far back in the mine, and the 
track bonding was also overhauled and 
rails put in condition: but the troubles did 
not disappear entirely until a 500 kw., 600 
volt direel current steam turbo-generator 
was installed in the Thomas power house. 
This turbine has demonstrated the particular 
suitability of this type of prime mover for 
handling tin- enormous fluctuations in load 



ELECTRICITY IN THE MINES OF THE DAVIS COAL AND COKE CO. 



which occur in mining work. The norma] 
current of this machine at full load is 833 
amperes, but the unit is continually called 
upon to handle variations from to L450 
amperes, which recur sometimes at intervals 
of a minute or less, when a train is picking 
up cars at the far end of the mine. The 
installation of prime movers possessing suffi- 
cient steadiness to stand up to this severe 
requirement has resulted in the entire 
disappearance of the former frequent burnouts 
i if mi in ir armatures. 

The electrical apparatus in the power house 
at Thomas comprises two 100 kw., single-phase 
alternators with tub transformers for town 
and house lighting; one 200 kw., three-phase, 
C>0 cycle alternator for supplying power to 
motors operating endless belts in the breaker 
and those operating the pumps, of which 
there are four 5 in. suction 4 in. discharge, 
! in. suction '2Yi in. discharge, one (i in. 
suction 5 in. discharge, and one 10 in. suction 
with 8 in. discharge. All of these motors are 
designed for operation at 550 volts. The 
direct current equipment consists of one 
204 kw., 000 volt and one 136 kw., 600 volt 
General Electric generator. The 500 kw. 
Curtis turbine provides current for eight 
13 ton and one 20 ton General Electric 
locomotives, and the coke larries. 

Air. L. S. McDowell is superintendent of 
this division. 

In the Coketon division, one mile west of 
Thomas, mines Xos. 35, 36 and 37 are operated 
in the lower Kittanning seam. This coal 
comes to the surface at a good height for 
tipples with drift openings. Nos. 24 and 26 
are operated in the same group on the upper 
Freeport scam. The mines at Coketon are 
all equipped for electric operation throughout. 
Five 14 ton. two 13 ton and two 10 ton 
locomotives, as well as four I ' 2 ton gathering 
locomotive's and two electrically operated 
coke larries, are upplied with current from 
two 250 kw., 600 voll generators of the 
belted type. A inn kw. Curtis turbine direct 
current and a 300 kw. Curtis 

turbine alternator supply current to this 
mine. There is also an older General Electric 
Form "D" alternator which 1m < < h hard 
service for many years . "4 ran now be used 



eit her as additii >nal power, running in multiple 
with the turbines, or, by simply dropping off 
tin lull and starting from the turbine-. .1 a 
motor, ran be used as a rotary condenser for 
improving the power factor of the system. 
At Coketon there are two pumps of id in. 
suction 8 in. discharge, two of li in. suction 
5 in. discharge, and two of 5 in. suction I in. 
discharge. Idle fans a! Coketon are also 
electrically driven. Mines Xos. :!."> and 36 
are connected with mine No. 34 at Thomas, 
and No. 35 is therefore ventilated by a split 
from No. 34, while No. 36 is ventilated by a 
1.") foot Crawford and McCrimmon fan 
driven by a variable speed induction motor. 
Mine No. 26 is ventilated by a similar unit. 

Practically the entire output of these mines 
is used for the manufacture of coke, the 
remainder being shipped West for smithing 
purposes. There arc 500 ovens here and all 
are charged electrically. The coal that is 
shipped West for smithing purposes is loaded 
in box cars with box car loaders driven by 
alternating current motors. 

The power house is further equipped with 
two Norwalk air compressors for the coal 
punching machines. Mr. M. L. Garvej is 
superintendent . 

The next group of mines at Weaver, 
Randolph County, consists of Nos. 1, 2 and 3 
in the lower Kittanning lied, which here 
shows up 9 feet thick and provides an 1 
lent coking coal. The three mines are 
operated by gravity rope haulage and have 
235 coke ovens. Mr. W. \Y. Brewer is 
superintendent of this section. 

The main office of the operating department 
is located at Thomas, W. Va., where Mr. Lee 
Ott, the general superintendent, resides. 
Mr. Ott has been with the company for many 
years and has, therefore, seen the company 
expand territorially and make great pro 
along technical lines. The former of these is a 
simple process, bu1 to guide an undertaking 
of this magnitude in such technical channels, 
that all the best and most improved inven- 
tions and developments in the engineering 
world can be made available and used without 
accumulating a huge scrap heap at a large 
expense, 1 an achieA ement which require 
unusual foresight and judgment. 



GENERAL ELECTRIC REVIEW 



THE 1200-VOLT RAILROAD- A STUDY OF ITS VALUE FOR 

INTERURBAN RAILWAYS* 

By Charles E. Eveleth 



The various 1200-volt interurban railways 
have now been operating a sufficient length 
of time to prove that there are no material 
objections to the use of this voltage on 
passenger cars. The nature of such minor 
difficulties as have been experienced have been 
such that their correction has required only 
detail changes of design which have been 

dily made. The important items of 
reliability and low cost j»f upkeep have met 
all expectations. 

A single statement regarding the motors 
may explain the reason for this successful 
performance. On the Pittsburg, Harmony. 
Butler & Newcastle line, where the service is 
unusually severe on account of unusual 
grades and curves, a considerable number of 
the brushes originally shipped in the motor 
brush-holders are still in service, though 
many motors have now run over 150, 000 car 
miles, and the wear on the commutators is 
hardly perceptible. It can be stated from the 
performance of the 1200-volt system that 
nothing is jeopardized by the adoption of 
this system, and such economies as are 
possible by its use can generally be obtained 
without offsetting disadvantages. 

We may therefore assume that the 1200- 
volt system has "found itself* and a new 
system is thereby made available for consider- 
ation when studying the requirements of new 
railroads or extensions to existing systems. 
If desired, the cars may be run at equal 
efficiency over tracks equipped for 600 volts. 

This being the case, the question naturally 
arises, what gains may be expected from the 
if this higher voltage? 

The primary ! any railway is to pay 

dividends and these an' limited by the amount 
of receipts which must be expended for two 
items fixed charges and operation. The 
most inflexible item is fixed charges. This 
works twenty-four hours a day whether 
business is good or bail and never gives up 
any ground o aed. Its only vulnerable 

point is tin- first cost of the railway. The 
I200-vol1 system now offers a practical way 
of reducing the first COSl of electrification 
through the material saving in substations 
and secondary distribution ci nductors. This 



*A paper presented before the Philadelp of the 

American Institute of Electrical Engineers, on January HI. 
1910. 



gain becomes a permanent asset of the railroad 
making a definite decrease in the fixed charges 
at a place which cannot be reached in any way 
except by raising the voltage. 

The other item is cost of operation. This 
item may be controlled to a certain extent 
by the personal ability of the manager, but 
having once selected the type and size of 
cars and the voltage of the system it is 
practically impossible for him to materially 
change the cost of getting power to his cars, 
which depends upon the distribution efficiency 
of his system and the cost of substation 
operation. The 1200-volt system decreases 
the cost of getting power to the cars in two 
ways: first, reducing the number of sub- 
stations, and second, increasing the substation 
efficiency by improving the load factor. This 
latter result may seem unreasonable at first 
thought until one considers upon what grounds 
substation units are selected. They an' not 
selected on the basis of heating, for it is 
probable that there are few interurban 
stations in this country running with 50 per 
cent, average load factor, and the average 
is certainly below :!n per cent, for the ordinary 
interurban conditions. It is generally neces- 
sary for the station unit to commutate within 
its overload guarantees, the maximum start- 
ing current of at least two trains starting 
simultaneously. As the running current of a 
train is about one-third of the starting current, 
and there are considerable periods during 
coasting and stops when the train is taking 
no current, and, furthermore, there are 
generally times when no trains are on the 
section fed by an individual substation, the 
low load factor can readily be accounted for. 
If then the units are selected for neak condi- 
tions the capacity of each station will remain 
constant, independent of the number of 
stations. It is evident when decreasing the 
number of substations, that is. increasing the 
track mileage fed by each station, that the 
average load will be greater and the sub- 
station load factor and efficiency improved. 
The total substation cost and operation will 
In- decreased practically in proportion to the 
reduction in the number of stations. These 
advantages tire net advantages since they 
are. in the 1200-volt system, obtained without 
being offset by extraordinary car equipment 
maintenance. 



L200-VOLT RAILROAD 



27 5 



DESCRIPTION OF RAILROADS 



Length of road, miles, all single track 
Time between trains each direction, minutes 
Cars per train .... 
Seating capacity per ear 
Distance between stops, miles 
Schedule speed, miles per hour 
Maximum speeds, miles per hour 
Car-miles per day 



100 

60 

3 

65 

5 

45 

60 

9000 



100 
60 

1 
60 

35 

48 

3000 



100 
60 

1 
50 

1 
25 
38 

.-0(111 



D 

100 

60 

1 

40 

0.5 
15 
28 
••Klllll 



Any railway is complex, but there are 
certain fundamental differences, namely, track 
mileage, size of trains units and schedule 




Fig. 1. Intcrurban Railway Systems. Single Track. Length of Road 
100 Miles. Cars Every Hour in Each Direction. 

speeds, which have a definite influence on the 
cost of electrification. In order to obtain 
an idea of the advantages which may be 
expected with the use of 120(1 volts as con- 
trasted with 600 volts, let us consider some 



concrete applications to different classes of 
conditions from which we may be able to 
draw some general conclusions. (Table 
above, i 

In making these comparisons conservative 
values have been used, such as low substation 
cost, high cost of 1200-volt car maintenance, 
etc., so that the results will be conservative 
and the advantage rather less than might 
actually be achieved. 

It will be seen that the roads vary greatly 
in conditions, from the heavy railroad condi- 
tions of A, through heavy interurban B, light 
interurban C, and very light traffic D. In 
fact, the cars of D will be no heavier than 
many city cars. ( See also Fig. 1 ) . 

Cars. Based upon the requirements, the 
data in the table below may be considered 
reasonable for the cars: 

It will be noticed that the power consump- 
tion which is "at the train" is slightly more 
for the 1200-volt cars on account of the 
greater weight of their equipments. 

In the first table on following page, 1(1 per 
cent, greater maintenance is allowed for the 
upkeep of the 1200-volt electrical equipment. 
As a matter of fact, up to the present time 
no noticeable increase has been observed. 

Substations. In selecting the size of syn- 
chronous converter units for the stations, 
they are in this case based on a maximum 
momentary demand of two cars starting 
simultaneously, except in the ease of system I 





CARS— GENERAL 


DATA 














A 


B 


C 


600 


D 




1200 


800 


1200 


600 


1200 


' 


600 




Volt 

CO 


Volt 
60 


Volt 


Volt 


Veil 


Volt 




Volt 


Number 


15 


15 


17 


17 


20 


20 


ach 


$15,000 


$13,000 


$1 1,000 


$10,000 


$8,000 


$7,000 


$5,000 


St.. Mm 


Weight, tons .... 


,■;.:, 


45 


36 


35 


27 


26 


IS 


17 


Amperes starting 


1200 


2200 


281 1 


520 


200 


370 


120 


2 'i' 


Amperes run 


300 


574 


!U 


171 


66 


121 


Ml 


71 


Kw-hr. per train mile 


11.16 


10.8 


2.88 


2. so 


L.89 


1.82 


1.08 


1.02 


( ar-miles per day per car 


150 


1 51 1 


200 


200 


l ,6 


\;r, 


150 


150 



276 



GENERAL ELECTRIC REVIEW 



where the size is based on the demand of 
one train starting and one train running. 
In each case a reasonable margin is allowed 
for occasional additional service. 

The number of substations is dependent 
upon the maximum economical spacing, 



The actual amount should be somewhat 
greater than these values, for with the 
addition of a substation there is a reduction 
in load factor on each substation, lowering 
rlie distribution efficiency. A curve is given 
(Fig. 2) to show the change in sul>" 



CARS— COST OF MAINTENANCE 
Cents per Car- Mile 





A 




B 


C 




D 




1200 
Volt 

L.25 

.99 


600 

V. It 


1200 
Volt 

[.00 


600 
Volt 


1200 
Voll 


600 
Volt 


Vi 1' 


l nical 
Electrical 


1 25 
90 

2.15 
$70,500 


Mill 
.7(1 


Mil 

60 


.'.in 
.55 

1.47) 
$17,1 


.77, .77, 
.7,(1 


Total . . . . 
cost 


2.24 
$73,500 


1.77 
$19, 4(1(1 


1.7(1 
sls.uOO 


1.7,(1 
Mi',, inn 


1.30 1.25 
$14,300 S13. 7(1(1 



Numb ,ns 

momentary demand, 
Number of units 
Size of each unit 
Cost of t ,ii ii m, i 



kw. 





\ 


B 

IL'im I.I in 


lL'HI) 


600 


D 


IL'IIII 


hi in 




Volt 


Volt 


Volt 


Voll 


Volt 


Volt 


Volt 


6 


14 


1 


ii 


6 


:; 


1-1 Id 


1320 


us in; 


370 


:;im 


250 


2 


2 


2 2 


2 


2 


2 


l.diid 


1,1 II III 


:;iki 300 


200 


l'(l(l 


17,(1 


$60,000 


$56,000 


$26,400 


$24,000 


$20,200 


M.S. (IN' 


$17,100 



rum 



7, 

2! ii i 

■j 

I 7,1 1 
$15,600 



considered m conjunction with the cost of 
ler copper and the allowable line drop 
with the assumed conditions of load. In each 
case it will be found that the addition of 
another substation to the number given in the 
data will not save its equivalent in cost of 
eeder copper. This brings up the question 
as io what may be considered equivalent 
feeder copper. Tin- table below gives these 

equivaleiii : 



efficiency with change in the load factor on 
individual synchronous converters. This 
curve is for a station having 150 kw.to 300 kw. 
unit. For the larger machines the curve 
would be about two per cent, higher. 

ii will be seen thai the investment in 
feeder copper which must be savcil to justify 
an additional substation will be approximately 
'-"■j times tile eosl of the substation. 

An examination of the diagram (Fig. 3) 



EQUIVALENT FEEDER COPPER TO REPLACE ONE SUBSTATION 



Annual cost of labor 

rial 
Fixed charges 

[nterest 

Dep i 

Taxes and insurant 


in.l mate- 

7,', 
:e 


Total . 


11 ', 


Total 
Poi fei der copper th 
etc., will be appro 
cent. I: 


■ intei 

8 ! , per 
in fi 


[mi equivalent 
substa. will be 


tc 



Ii 



200 







,00 







10 






IL'IIII 



$9,100 



si, mm $1,900 -i R00 $1,800 $1,700 



6,160 


2,904 


2,640 


2.222 


$8,760 




$4,022 


in;. in in 


- - 100 




- -.sun 



2,024 
$3,824 



' 881 
$3,581 



linn 



SI, 71 ii I 



1.716 



$46,400 $43,400 $41,400 



200-YOLT RAILROAD 



277 



showing the "location of substations" will 
give a fairly comprehensive view of the rail- 
road layout and the location of the cars at 
any hour. 

Primary Distribution. This in each case 
will be the same for either system, 
except that the total length of the 
600-vol1 transmission , line will be 
slightly Longer on account of the 
greater distance between the terminal 
stations. A Hat price of $3,500 per 
mile of transmission line is taken for 
system .1. and $1,000 per mile for 
systems B, C and D. 

It will make practically no dif- 
ference where the power is fed to the 
high tension system. For the sake 
of simplicity it is assumed that power 
is purchased and delivered to the 
power house step-up transformers at 
one cent, per kw-hr. 

Sei ondary Distribution. Track. For 
railroad .1, 85 lb. rail is assumed. 
This has a resistance per mile, includ- 
ing bonding, of approximately 0.033 
ohm. The other roads use 70 lb. rail 
having a resistance per mile of 0.04 
ohm. A third-rail equivalent to a 
1,000,001 i-cir-mil. feeder is assumed 
for. 1, and No. 0000 trolley wire for 
the other roads. The values used in 
obtaining the feeder copper neces- 
sary are based on a momentary 
maximum emergency drop of 250 
volts for the 600-volt systems and 
500 volts for the 1200-volt systems. 



This will give an average econdary distribu- 
tion efficiency of approximately 90 per cent, 

In electrification material there is included 
under "first cost" and "fixed charges," 
(I and II) cars and car equipments, sub- 





JO0 
















1 












q$ 




























































<?<f 






























51? 






























SO 




























1, 


9f? 




























,<i 


flA 




























^ 










/ 




















1 




























































$ 

Kl 


































































/ 






























/ 






























1 


























i 


' / 


? 2I0 3 

Cdnvc. 


7 4 


7 5 

r I 


7 6 
■>aa 


7 7 
Fa 


7 d 
cto 


7 so 100 1,0 n'o 

r - Perce/71 



Fig. 2. Rotary Converter Sub-Station Efficiency Curve 



FEEDER COPPER REQUIREMENTS 





1200 Volt 


600 Vol 


1200 Volt 600 Vol 


Volt 


600 Volt 


120(1 Voll 


1 \..i 


Stub End ( 'nil illations: 












Train, starting and running 




1-S 


1-S 


1-S 1-S